Complete Guide to Door Mechanisms

Door mechanisms are at the heart of your entrance security and day‑to‑day convenience. Whether you are a trade installer, locksmith, facilities manager or a competent DIYer, understanding how a multipoint door lock, door gearbox and euro cylinder work together will save time, reduce call‑backs and help you choose the right replacement first time.

This guide focuses on modern UK domestic and light‑commercial doors, particularly uPVC and composite entrance doors, aluminium doors and some timber doors that use a multipoint door lock. It covers the main lock types, euro cylinder compatibility, how to measure accurately, leading brands, and practical installation tips.

Throughout this guide you will find references to our door mechanisms and specific product groups such as multipoint locks and euro cylinders to help you source the correct parts quickly.

1. Multipoint lock types

1.1 What is a multipoint door lock?

A multipoint door lock (often called a multi‑point locking system or strip lock) is a long locking mechanism fitted into the edge of the door. It typically has:

A central door gearbox containing the main latch and deadbolt

A long faceplate (strip) running most of the height of the door

Additional locking points such as hooks, bolts, rollers or mushroom cams

A euro profile cylinder (usually) to control the mechanism

Door handles and a spindle to operate the latch and locking points

When you lift the handle, the multipoint door lock engages several locking points into matching keeps in the frame. Turning the key (or thumbturn) then deadlocks the mechanism. This provides better security and weather sealing than a simple single‑point mortice or nightlatch.

Multipoint locks are now standard on:

uPVC front and back doors

Composite doors

Many aluminium and steel entrance doors

Some modern timber doors with euro cylinder operation

The two most commonly replaced components are:

The door gearbox – the central case that contains the latch, deadbolt, follower(s) for the handle spindle, and the cam interface for the euro cylinder. Gearboxes can fail due to wear, misalignment or forced entry attempts.

The euro cylinder – the keyed cylinder that controls the multipoint lock mechanism. Upgrading to an anti‑snap cylinder is a frequent security improvement.

1.2 Types of multipoint lock by operation

Multipoint locks are classified partly by their operating function – how the handle and key interact with the mechanism. Common types include:

Lever/Lever (Standard Operation)

This is the most common arrangement on uPVC and composite doors.

Handles on both sides are lever type

Depressing the inside or outside lever retracts the latch and auxiliary locking points (when not deadlocked)

Lifting the handle engages the hooks/bolts/rollers

Turning the key deadlocks the mechanism so the external handle no longer retracts the lock

Suitable for: Most domestic front and back doors where standard operation is acceptable.

Lever/Pad (or Offset Pad)

Often used on front doors where the customer wants the door to latch shut from outside without being left unlocked.

Inside: normal lever handle

Outside: short pad handle (or offset lever) that usually only operates the latch when the door is not locked by key

Once locked with the key, the outside pad will not open the door; key operation is required

This gives a similar feel to a traditional nightlatch but using a multipoint door lock.

Split Spindle (Day Latch Function)

Some lever/lever and lever/pad locks have a split spindle gearbox.

The internal and external spindles are separate and perform different actions

The external handle may only operate the latch in certain modes (e.g. until first locking)

Common on doors where the customer wants the door to “slam shut” and latch from the outside

Correct spindle configuration is critical when replacing the door gearbox on split spindle systems.

Key Wind (Key‑Operated Only)

Instead of using the handle to throw the bolts/hooks, a key‑wind multipoint door lock uses the key to wind out the locking points.

No lifting handle action is used to engage the locks

Often seen on older or more specialist doors, including some timber and aluminium sets

Operation can be slower but is considered robust and is less prone to alignment‑related handle stiffness

Automatic and Slam‑Shut Multipoint Locks

Modern high‑security composite door lock systems may use automatic or slam‑shut mechanisms.

Closing the door automatically throws hooks or bolts without lifting the handle

Some use magnets or mechanical triggers in the frame to engage the locks

Often combined with a high‑security key cylinder and PAS 24 / Document Q‑compliant door sets

These are popular on premium composite and aluminium entrance doors.

1.3 Types of multipoint lock by locking points

The type, number and position of locking points vary. Common arrangements include:

Hooks

Hook bolts pivot out of the faceplate and engage into keeps in the frame

Provide strong anti‑jemmy resistance by “hooking” behind the keep

Typical configurations: two hooks (above and below the latch), or hooks plus rollers

Deadbolts / Linear Bolts

Rectangular bolts shoot straight out from the faceplate

Provide positive engagement and good compression

May be used in combination with hooks or on their own

Rollers and Mushroom Cams

Rollers: rounded cams that adjust for compression and assist with weather sealing

Mushroom cams: shaped cams that offer some anti‑lift protection

Usually accompanied by primary hooks or bolts for security

Rollers and mushroom cams are often adjustable using an Allen key to fine‑tune door compression.

Shootbolts and Top/Bolt Extensions

Additional rods that extend upwards into the head of the frame or down into the threshold

Used commonly on French doors, double doors or high‑security doors

May be operated by the same handle or by a separate flush bolt

1.4 Door types: uPVC vs composite vs aluminium vs timber

While the basic principle is the same, the multipoint door lock and composite door lock systems vary by door material.

uPVC doors

Most common use of multipoint locks

Faceplate widths typically 16 mm or 20 mm

Backsets commonly 28 mm, 30 mm, 35 mm or 45 mm

Rollers plus hooks or bolts for compression and security

Composite doors

Composite door lock systems are designed to suit thicker, more rigid door slabs and often to meet higher security standards.

Faceplate usually 16 mm, 20 mm or a U‑channel type

Backsets typically 35 mm, 45 mm or sometimes 55 mm

Commonly use multiple hooks/bolts and sometimes automatic locking

Frequently PAS 24 and Document Q compliant when used in a tested door set

Aluminium doors

Use slimmer or specially profiled multipoint locks

Backsets can be smaller (e.g. 25 mm) due to narrow profiles

Often require manufacturer‑specific mechanisms and keeps

Timber doors

Some modern timber doors use multipoint locks with larger backsets (45–60 mm)

Faceplates may be 20 mm or wider

Timber can be more forgiving for minor adjustments but requires precise routing

1.5 Key dimensions and terminology

When identifying or replacing a multipoint door lock, you will frequently encounter the following key terms:

Backset – distance from the faceplate edge to the centre of the key cylinder (or spindle on some locks). Common sizes: 25, 28, 30, 35, 40, 45, 55 mm.

PZ (centres) – distance from the centre of the handle spindle to the centre of the key cylinder (euro). Most common is 92 mm, but 68 mm, 70 mm, 72 mm and 92/62 mm split PZ exist.

Faceplate width – width of the visible metal strip on the door edge. Typically 16 mm, 20 mm or 24 mm.

Overall length – full length of the strip from top to bottom; useful but less critical, as many strips can be cropped to size.

Centres of locking points – distances between latch/bolt centre and hooks/rollers for matching to existing keeps.

Getting these measurements right is critical when ordering a replacement from our range of multipoint locks or standalone door gearboxes.

2. Euro cylinder compatibility

2.1 What is a euro profile cylinder?

The majority of modern multipoint locks and composite door lock systems use a euro profile cylinder. This is the removable keyed barrel that passes through the door and into the door gearbox.

Euro cylinders provide:

Keyed access from one or both sides

Compatibility with a wide range of multipoint mechanisms

Easy upgrading without changing the full lock

Common types include:

Double cylinder – keyed both inside and outside

Thumbturn cylinder – key outside, thumbturn inside

Single cylinder – keyed on one side only (e.g. garage side doors)

2.2 How the euro cylinder and gearbox work together

The euro cylinder has a rotating cam in the middle. When the correct key is turned, the cam rotates inside the door gearbox.

The cam engages with the gearbox’s locking mechanism

Turning the key after lifting the handle deadlocks the hooks/bolts

Turning the key the opposite way releases the deadlock, allowing the handle to retract the lock

For a door lock mechanism to operate smoothly:

The euro cylinder length must be correct for the door thickness and furniture

The cam must be the correct type (standard euro cam in the vast majority of UK multipoint locks)

The screw fixing hole must align with the gearbox’s cylinder fixing hole

Almost all standard uPVC and composite door lock gearboxes use a standard euro cylinder. However, always check for unusual or specialist profiles before ordering from our euro cylinder range.

2.3 Security standards and anti‑snap protection

In the UK, front door security has improved significantly with the introduction of anti‑snap euro cylinders, driven by burglary techniques that targeted weak cylinders on uPVC doors.

Relevant UK standards and schemes include:

BS EN 1303 – European standard for cylinder performance (durability, security, corrosion, etc.)

TS 007 – Kitemark standard defining 1‑star and 3‑star cylinder security levels

Secured by Design – police‑preferred specification that often requires 3‑star or 1‑star plus 2‑star hardware

PAS 24 – enhanced security performance standard for door sets (the whole door assembly, not just the cylinder)

Anti‑snap cylinders are designed so that if an intruder attempts to break the cylinder, it will snap at a sacrificial section without exposing the cam. The lock remains secure and still operable with the correct key.

Common anti‑snap brands available through the Window Hardware Store include:

Yale (Yale Platinum 3‑Star, Yale Superior, etc.)

ERA (ERA Invincible, ERA Fortress)

Avocet (ABS 3‑Star)

Mila (ProSecure, ProSecure 2)

When upgrading a multipoint door lock or composite door lock, it is good practice to install at least a TS 007 1‑star cylinder, and preferably a 3‑star cylinder if budget allows, especially on primary entrance doors.

2.4 Cylinder length and offsets

Cylinder length is one of the most important compatibility factors. Euro cylinders are measured overall in millimetres, but described as two halves from the centre of the fixing hole:

Example: 45/50 (95 mm) – 45 mm from the fixing hole to the inside end, 50 mm to the outside end

To measure an existing cylinder:

Remove the fixing screw from the faceplate (usually located below the latch)

Turn the key slightly to align the cam so the cylinder can be withdrawn

Measure from the centre of the fixing hole to each end in mm

The cylinder should not protrude excessively beyond the handle backplate. As a rule of thumb:

Ideal: Cylinder ends are flush with, or up to 1–2 mm proud of, the backplate

Poor: Cylinder protrudes more than 5 mm beyond the handle, creating a security weak point

Some doors require offset cylinders because the door thickness and furniture design mean the inside and outside requirements differ. This is especially common on composite doors with decorative external furniture.

2.5 Thumbturn vs double cylinder

Building regulations and fire safety guidance often recommend the use of internal thumbturn cylinders on escape routes so that occupants can exit quickly without a key.

Thumbturn cylinders are strongly recommended for flats and HMOs on exit doors, subject to the fire strategy

Document B (Fire Safety) and guidance from local fire services may influence cylinder choice

On some doors, such as those opening onto communal escape routes, additional rules may apply – always check with the responsible person or fire risk assessor

For most domestic houses, a thumbturn on the main door is a convenience and safety feature rather than a strict requirement, but is widely adopted.

2.6 Special profiles and compatibility notes

While standard euro profile cylinders fit the vast majority of UK multipoint locks, there are some exceptions:

Oval profile cylinders (less common on modern uPVC/composite doors)

Specialist aluminium systems with proprietary cylinders

High‑security door sets where the cylinder is integral to a certified package

If your door has an unusual cylinder shape, photograph it and compare with the options in our euro cylinder category, or contact us for advice before ordering.

3. Measuring for replacement

Accurate measurement is essential when replacing a multipoint door lock, door gearbox, or euro cylinder. Incorrect sizing can lead to poor operation, security issues, and wasted time on site.

3.1 General measuring tips

Always measure in millimetres (mm)

Use a steel tape or vernier calliper for accuracy

Take clear photos of the existing lock in the door and once removed

Note any brand markings or codes on the faceplate or gearbox

Measure at least twice before ordering from our door mechanisms range

3.2 Measuring a complete multipoint lock

When replacing the full multipoint strip rather than just the gearbox, note the following:

Backset – Remove the lock (if possible) and measure from the faceplate edge to the centre of the keyhole / cylinder cut‑out. Common values: 28, 30, 35, 40, 45, 55 mm.

PZ (handle centres) – Measure from the centre of the handle spindle to the centre of the keyhole (euro cylinder). Common PZ sizes: 92 mm, 70 mm, 72 mm; lever/pad sets may have 92/62 mm split PZ.

Faceplate width – Measure across the visible metal strip on the door edge: 16, 20 or 24 mm are typical.

Overall length – From the very top of the strip to the very bottom. Many strips are 1500–2200 mm, but exact length is often less critical because ends can sometimes be cropped carefully (check manufacturer guidance).

Position of locking points – Measure from the centre of the latch to the centre of each hook, roller or deadbolt. This is vital to ensure your existing keeps line up with the new lock or that new keeps can be positioned without fouling hinges or glazing.

Locking point types – Note whether hooks, rollers, mushrooms, linear bolts etc. are present and how many of each.

Handing – Some locks are handed (left/right). Check which way the latch faces and whether it is reversible.

Trade tip: If you’re unsure about the brand or model, lay the removed mechanism flat, take a photo with a tape measure in view, and compare against images in the multipoint locks section. Many locksmiths and installers keep a small reference library of common patterns for quick identification.

3.3 Measuring the door gearbox

Sometimes it is more economical and faster to replace only the central gearbox rather than the entire strip, particularly on well‑known systems (ERA, Yale, Mila, Avocet, GU, etc.).

To measure the gearbox:

Backset – As with the complete lock, measure from the faceplate edge to the centre of the keyhole/spindle hole inside the case. Typical sizes 28–45 mm.

Case height and width – Measure the main body of the gearbox (excluding the faceplate). This helps match to specific models.

Follower arrangement – Count and measure any handle spindle followers (square holes). Some gearboxes have twin followers, split spindles, or offset followers for lever/pad operation.

Fixing screw positions – Note the distances between the faceplate fixing screws around the gearbox; replacement gearboxes from different series may not line up.

PZ – Confirm the spindle‑to‑cylinder centre distance again at the gearbox.

Gearboxes are often marked with a logo or code (e.g. ERA, Yale, GU, Lockmaster, Mila). Use these markings in combination with your measurements to select a matching gearbox from our door gearbox range.

3.4 Measuring a euro cylinder

As outlined earlier, euro cylinders are measured from the centre of the fixing screw hole:

Remove the cylinder from the door by undoing the retaining screw on the faceplate and turning the key to withdraw the cylinder

Measure from the centre of the fixing screw hole to each end: inside and outside

Record as e.g. 40/40 (80 mm), 35/45 (80 mm), 45/50 (95 mm)

Also note:

Thumbturn or double cylinder

Finish (e.g. nickel, brass, black, chrome) to match existing door furniture

Security rating (TS 007 1‑star or 3‑star, BS EN 1303, etc.)

Pair your cylinder measurement with the correct product in our euro cylinders section. For a typical modern composite door lock on a 44 mm–48 mm thick slab, common sizes are 45/45 (90 mm), 40/50 (90 mm) or similar, but always confirm on the actual door.

3.5 Measuring door handles and PZ centre

Handles work hand‑in‑glove with your door lock mechanism. Poorly matched handles can put undue stress on the gearbox and cause premature failure.

When replacing handles:

Measure PZ – centre of the keyhole to centre of the spindle hole (e.g. 92 mm)

Measure fixing screw centres – distance between the handle fixing screws. Some sets use 122 mm, 210 mm or other spacings.

Note handing – some lever/pad handle sets are handed left or right

Record the plate length and width if aesthetics are important

Match these to replacement handles in our door handles category to ensure they work smoothly with your existing multipoint door lock.

3.6 Allowing for tolerances and adjustments

Most multipoint systems have some adjustability built in:

Rollers and mushroom cams may be adjustable by ±1–2 mm to fine‑tune compression

Keeps/strikers can often be moved slightly within the frame or packers changed

Handles may have slot‑type fixing holes to allow for slight misalignment

However, do not rely on adjustment to compensate for a fundamentally incorrect lock size. If in doubt, re‑measure or contact us with photographs before ordering.

4. Common brands

Recognising common UK door hardware brands can significantly speed up identification and replacement. Below is an overview of leading multipoint door lock and composite door lock manufacturers you will encounter in the UK market.

4.1 Yale

Yale is one of the most recognisable names in locks, with a wide range used on uPVC, composite and timber doors.

Common on both older and newer installations

Distinctive Yale branding often stamped on the faceplate or gearbox

Offer both full multipoint strips and replacement gearboxes

Supply standard and high‑security euro cylinders (e.g. Yale Platinum 3‑Star)

Yale composite door lock systems are widely used by door manufacturers seeking PAS 24 and Secured by Design compliance, especially when paired with 3‑star cylinders and security handles.

4.2 ERA

ERA produce a wide variety of door mechanisms for uPVC, composite and timber doors.

Look for the ERA logo or codes on the faceplate

Offer single and dual spindle gearboxes, split spindle versions and hook/roller configurations

Popular on both trade‑fabricated and branded door sets

Provide anti‑snap cylinders and high‑security furniture to complement their locks

ERA locks are frequently used on PAS 24‑rated door sets when combined with tested keeps and reinforced frames.

4.3 Mila

Mila (Mila Hardware) supply a range of premium hardware to the window and door trade.

Common on trade uPVC and composite doors

Offer robust gearboxes and full strip mechanisms

Signature features may include twin hooks with adjustable rollers

Mila ProSecure cylinders and handles are popular security upgrades

Mila mechanisms are known for their smooth operation and are a good option for both new installations and replacements specified via our multipoint locks collection.

4.4 Avocet

Avocet is well known for both its multipoint locks and ABS anti‑snap cylinder range.

Avocet multipoint locks often appear in uPVC doors from various fabricators

ABS 3‑star cylinders are a popular high‑security upgrade, often used to replace lower‑spec cylinders without changing the whole lock

Look for Avocet or ABS branding on cylinders and sometimes on the strip

Upgrading to an Avocet ABS cylinder is a straightforward way to enhance a door lock mechanism’s resistance to snapping and drilling.

4.5 GU (Gretsch‑Unitas)

GU is a major European manufacturer whose locks are widely used across the UK.

Commonly found on uPVC and composite doors, as well as some aluminium systems

Usually identifiable by “GU” stamped into the faceplate

Extensive range of hooks, bolts, rollers and auto‑locking variants

GU composite door lock systems are particularly common on European‑style doors and those supplied in higher‑end door sets.

4.6 Winkhaus

Winkhaus (often stylised as WINKHAUS) supply advanced multipoint locking systems.

Popular on premium composite and timber entrance doors

Known for auto‑locking and slam‑shut systems such as AV2 and AV3

Often part of PAS 24, Document Q‑compliant door sets with specific keeps and cylinders

When replacing a Winkhaus lock, it is important to match the exact model and consider the certified status of the door set if it is part of a tested system.

4.7 Lockmaster / Safeware

Lockmaster (and associated Safeware branding) is widely used across UK uPVC doors, including patio and French doors.

Often feature hooks with additional rollers

Available as full strips and standalone gearboxes

Sometimes rebranded for specific window and door fabricators

Replacement Lockmaster gearboxes are commonly used by locksmiths as they can often be swapped without changing the keeps.

4.8 Fullex

Fullex is another established manufacturer with a solid presence in the UK.

Offer high‑security multipoint locks for uPVC, composite and timber doors

Many Fullex systems feature twin hooks and centre deadbolts

Used on PAS 24 and Secured by Design‑compliant door sets

4.9 Maco, Roto and Others

Maco, Roto, Ferco, Securistyle and others also appear frequently, especially on European‑origin or specific fabricator door systems.

Maco: Widely used in both windows and doors; multipoint locks often with mushroom cams and hooks

Roto: Strong presence in aluminium and some timber/uPVC installations

Ferco: Found on older systems and some French doors/patio sets

Each brand has its own range of gearboxes, backsets and PZ sizes, so identification by marking and measurement is essential.

4.10 Identifying your lock brand

To identify the brand of your multipoint door lock or composite door lock:

Look for a stamped logo or name on the faceplate (e.g. ERA, GU, Yale, Mila, Avocet)

Check the gearbox for cast‑in lettering or stickers

Note any part numbers, date codes or certification marks (e.g. BS, PAS 24)

Compare the layout of locking points and case shape with images in our door mechanisms catalogue

Accurate identification allows you to order a like‑for‑like replacement or a compatible retrofit model, helping to minimise fitting time and avoid unnecessary frame or keep adjustments on site.

5. Installation

Replacing a multipoint door lock, door gearbox or euro cylinder can be a straightforward task for a competent DIYer, but some situations demand professional expertise. Below you’ll find step‑by‑step guidance, trade tips and common problem‑solving advice.

5.1 Safety, regulations and when to call a professional

Before beginning work:

Confirm whether the door is part of a certified fire door set or PAS 24 / Document Q‑compliant security door set. Replacing hardware with non‑approved components may invalidate certification.

For communal exit doors or fire escape routes, consult the responsible person or fire risk assessor before altering hardware, particularly with regard to thumbturns and panic hardware.

If you are unsure, or if the lock has failed with the door closed and access is restricted, consider engaging a professional locksmith or installer.

For standard domestic uPVC and composite doors, changing a lock is generally within the scope of a capable DIYer, especially when simply replacing a euro cylinder or a like‑for‑like multipoint mechanism.

5.2 Tools and preparation

Typical tools required:

Pozi and flat screwdrivers (long‑reach advisable)

Drill/driver with appropriate bits (for screws only, not for forcing locks)

Measuring tape (mm)

Pencil and masking tape

Allen keys (for roller/cam adjustment)

Lubricant (dry PTFE or graphite; avoid heavy oils and grease inside the gearbox)

Chisels and sharp knife (for minor timber adjustments only)

Preparation steps:

Open the door fully and support it if hinges are worn or loose

Engage the multipoint lock and observe where hooks/rollers align with keeps

Take photos of the existing setup for reference

Place screws and small parts in a tray to avoid losing them

5.3 Removing an old multipoint lock

To remove a full multipoint door lock strip:

Fully open the door

Remove the internal handle set: take out the two (or more) fixing screws, withdraw handles and spindle

Remove the euro cylinder: undo the cylinder retaining screw on the faceplate, insert the key, turn slightly to align the cam, and slide out the cylinder

Undo all screws along the faceplate securing the strip to the door edge

Gently pull the strip away from the door, starting at the gearbox; tilt and manipulate to clear the hooks and rollers from the mortice

If the door is bowed, swollen, or the lock is severely jammed, you may need to retract hooks manually by accessing the gearbox with the faceplate partially removed. Exercise care to avoid damaging the door.

5.4 Fitting a new multipoint door lock

Once you have selected a compatible replacement from our multipoint locks range:

Compare the new strip with the old one on a flat surface: check backset, PZ, hook/roller positions, faceplate width and length

If the new strip is longer and the manufacturer permits cropping, carefully cut to length at the designated crop points using a hacksaw, deburr edges and ensure moving parts are unaffected

Insert the strip into the door edge, carefully locating hooks/rollers in the existing recesses

Align the gearbox so that the spindle hole and cylinder hole line up with the door cut‑outs

Re‑fit the faceplate screws, working from the gearbox outward to top and bottom, but do not overtighten, especially on composite or uPVC skins

Next, re‑fit the cylinder and handles:

Insert the euro cylinder through the door and into the gearbox; ensure the cam engages properly

Secure the cylinder using the retaining screw from the faceplate; check that the cylinder is straight and not under stress

Insert the spindle(s) through the gearbox follower(s); on split spindle gearboxes, follow the manufacturer’s instructions for internal and external spindles

Offer up the handles, ensure they sit flush, then insert and tighten the fixing screws evenly

Test operation:

With the door open, operate the handle and key. Ensure:

The latch operates smoothly from both sides

Lifting the handle engages all hooks/rollers/bolts positively

Turning the key deadlocks and unlocks without excessive resistance

Only once you are satisfied with smooth operation should you close the door and check engagement with the frame keeps.

5.5 Replacing just the door gearbox

Replacing only the gearbox is often quicker and preserves the existing keeps and locking points.

Follow the removal steps as above, but once the strip is out, identify how the gearbox is fixed (usually with screws through the faceplate into the case)

Unscrew and separate the gearbox from the strip

Install the new gearbox, ensuring the latch orientation and spindle/follower arrangement match the original

Reassemble the strip and refit to the door

Pay particular attention to latch handing on some gearboxes; many have reversible latches that can be flipped by removing a clip or screw.

5.6 Adjusting keeps and door alignment

Even with a like‑for‑like replacement, small adjustments may be needed to achieve smooth closing and locking.

Check that the door is correctly aligned in the frame. Look at the margins (gaps) around the door – they should be even top, bottom and sides.

If the top of the door rubs on the frame, hinges may need adjustment or packing. Many modern hinges have lateral and height adjustments via Allen keys.

Check each hook/roller against its corresponding keep. Apply marker pen or masking tape to the keep, close and lock the door, then check where the marks appear.

Loosen the keep screws slightly and move the keeps in or out, up or down as needed to allow the hooks/rollers to engage fully but without excessive force.

Use the adjustment screws on roller cams or mushrooms to slightly increase or decrease compression. Turn clockwise to pull the door tighter to the gasket, anti‑clockwise to reduce.

Correctly adjusted, a door should:

Latch easily when gently pushed closed

Allow the handle to lift fully without undue force

Provide good weather sealing without needing to “slam” the door

5.7 Common problems and solutions

Stiff handle when lifting

Cause: Door dropped or bowed, misaligned keeps, over‑tight compression.

Solution: Adjust hinges to improve alignment; loosen and reposition keeps; back off roller compression slightly.

Key turns, but door will not unlock fully

Cause: Failed gearbox components (broken springs, worn cams), misaligned hooks under load.

Solution: Replace the door gearbox from our door gearbox range; check that hooks are not fouling the keeps.

Handle floppy or sagging

Cause: Worn handle springs, spindle wear, or damaged gearbox return spring.

Solution: Replace handles with sprung‑lever sets; inspect and replace spindle; if still sagging, replace the gearbox.

Door will not latch without slamming

Cause: Misaligned latch keep, bowed door, worn gaskets.

Solution: Adjust the latch keep closer or further out; check hinge adjustment; replace worn compression seals if necessary.

Cylinder turns 360° but no action

Cause: Incorrect cylinder cam engagement or broken internal gearbox linkages.

Solution: Remove and re‑fit cylinder, ensuring the correct length and full cam engagement; if still faulty, replace the gearbox.

Snapped or damaged cylinder

Cause: Forced entry attempt or over‑tightened handle screws compressing the cylinder.

Solution: Replace with a TS 007 3‑star anti‑snap cylinder from our euro cylinder selection; do not overtighten handle screws.

5.8 Special considerations for composite door locks

Composite door lock systems need extra care due to the nature of the door construction (GRP skins, dense foam or timber cores, and steel reinforcement).

Avoid overtightening screws into composite skins to prevent distortion or cracking

Ensure any replacement multipoint lock or gearbox is compatible with reinforcement positions in the door edge

When adjusting keeps, consider the threshold detail – many composite doors have low aluminium thresholds that interact with bottom bolts or hooks

Where the door is part of a PAS 24 or Secured by Design package, use manufacturer‑approved replacement parts to maintain certification

Composite doors are less forgiving of “making do” with incorrect parts; accurate identification and using appropriate components from our door mechanisms and multipoint locks ranges will reduce problems and call‑backs.

5.9 Lubrication and ongoing maintenance

Regular maintenance prolongs the life of any door lock mechanism:

Apply a light dry PTFE or silicone‑based spray to the latch, hooks, rollers and moving parts on the strip once or twice a year

Do not flood the gearbox with oil; a small amount of appropriate lubricant is sufficient, avoiding thick grease that can attract dirt

Use a graphite or specialist lock lubricant sparingly in the cylinder keyway; avoid WD‑40‑type penetrating oils as a long‑term lubricant

Check handle fixing screws periodically and tighten gently if loose

Inspect hinges for movement and re‑pack or adjust as necessary to maintain alignment

A well‑installed multipoint door lock paired with a quality euro cylinder and correctly set keeps should provide many years of reliable, secure service. When parts do eventually wear, replacing like‑for‑like or approved equivalents from our door mechanisms, multipoint locks, door gearbox and euro cylinder ranges will ensure continued compliance with UK standards and good day‑to‑day usability.