Guide
Types of Door Locks in the UK: What Each One Is and Where It Fits
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Every Door Lock Type in the UK at a Glance
The fastest way to name a lock is to look at the door it is fitted to, because the keyhole by itself rarely tells the full story. If a repair or replacement is on the cards, you may well be asked which type of lock you have before anything else. Look at the material of the door, where the mechanism is located, and what is visible on the inside face and the door edge. Distinguishing between a mortice lock, a nightlatch, a rim cylinder and a multipoint locking system is easier using those details.
| Lock family | Door it is usually fitted to | How it shows itself | The point to remember |
|---|---|---|---|
| Mortice deadlock | Timber entrance doors, chiefly | Its case is hidden in the door edge and the bolt shows when the door is open | It has a key-operated bolt and no latch moved by a handle in the same case |
| Euro cylinder with a multipoint lock | uPVC and composite doors are where it is common | A euro-profile cylinder near the handle and a long locking strip along the edge | The cylinder only accepts the key, while the wider mechanism works several locking points |
| Nightlatch with rim cylinder | Timber entrance doors, chiefly | A box case on the inside face, plus a cylinder visible on the outside | The latch usually locks itself into place as the door closes |
| Mortice sashlock | Timber doors at the entrance and inside the home | Its case is hidden in the edge, with a spring latch and locking bolt both showing | It combines a latch for the handles with a separate locking bolt |
| Surface-mounted rim lock | Some older timber doors, internal doors and outbuildings | Every part of the lock case can be seen on the inside face | It sits on the door surface instead of being recessed into the edge |
| Euro cylinder with a single-point lock | Some timber, aluminium and metal doors | A euro-profile keyway without the long strip or several locking points | The cylinder operates just one central lock case |
Lock names come from either the full mechanism or the part that takes the key, and that split is why people confuse mortice lock, nightlatch, euro cylinder and multipoint lock even though each describes a separate part or system. The table identifies the general family only. Modern timber doors can have multipoint systems, and aluminium and metal doors may use cylinder-operated lock cases, so material should never be read as proof. Before choosing replacement parts, the markings and measurements still have to be checked. This guide covers the common types in UK homes, how to recognise them, what their main components do and where markings can be found, and why appearance alone cannot confirm the exact model or security standard. Most identification mistakes happen in the two middle columns, so both are explained in their own sections below.
Locks Fitted Into a Timber Door
On timber, the lock is usually either inside the door edge or fixed to the inside face, and plenty of front doors have both. The quickest orientation check is the keyhole position: in the edge points to a mortice lock, while a key that goes through the face to a box on the inside points to a nightlatch. Timber doors commonly use mortice locks, nightlatches, surface-mounted rim locks or a mix of two separate systems, so check whether the case sits in the edge or on the face.
Mortice Sashlocks and Deadlocks
Where a key moves a bolt and there is no latch, the lock is a deadlock. Where handles work a latch and a key works a separate bolt, it is a sashlock.
Nightlatches and Their Rim Cylinders
A box on the inside face, with a rim cylinder visible outside, is normally a nightlatch that latches as the door closes. A traditional rim lock fitted to the inside face is not necessarily the same. It may house a latch, a bolt or both, may not latch automatically, and may be worked with a key, a handle or a knob.
Doors With More Than One System
A timber entrance door sometimes carries a nightlatch and a separate mortice lock. Because they operate independently, they should be identified separately, and neither is the better one, since each does its own job. A multipoint lock, a full system of connected parts usually found on uPVC and composite doors, is also used on some timber and aluminium doors, where locking points along the edge move into keeps on the frame.
Multipoint Locks Are Not One Type
A uPVC or composite door's locking strip extends along the height of the edge, and choosing another make is not a straightforward swap. The handle operates that multipoint strip through its mechanism; the key works the separate euro cylinder. Most enquiries about uPVC door lock types are really enquiries about the strip. Its identity depends on the manufacturer, geometry and locking-point arrangement together.
What the Strip Itself Tells You
Look at an open door and follow the strip away from its central latch and gearbox. Multiple rollers, hooks, pins or bolts along that edge usually indicate a multipoint. Some mechanisms combine several kinds. Matching keeps on the frame receive the latch and locking parts. Similar systems also serve some aluminium and timber doors.
| Detail to record | Why it helps identification |
|---|---|
| Faceplate lettering, symbols and stamped codes | Provides possible maker or model clues |
| Labels close to the latch | Adds references that may be absent elsewhere |
| Quantity and type of locking points | Distinguishes arrangements with different securing parts |
| Point shapes and spacing | Helps separate mechanisms that otherwise look alike |
| Position of the central gearbox | Shows how the main mechanism relates to the strip |
| PZ | Gives the distance between cylinder and handle spindle centres |
| Backset | Gives the distance from the faceplate edge inwards to the cylinder centre |
Photograph the entire edge as well as the handles, cylinder and readable markings. PZ and backset are useful identification clues, but identical values do not prove a match. Gearbox connections, faceplate details and locking-point positions can differ. A replacement order needs proper measurements; that task belongs to the separate guide about changing a cylinder.
The components have different jobs. A spindle crosses the door between its handles and carries their motion to the gearbox. The cylinder supplies keyed movement. The gearbox responds to these inputs and controls the points connected by the door strip beneath the faceplate. Keeps provide their receiving locations on the frame.
On a common handle-operated arrangement, raising the handle projects the locking parts and the key then prevents handle release. Alternatives include strips that engage automatically on closure and mechanisms whose points are driven with the key. Operation alone cannot confirm which make or model is present.
Avoid treating stiffness as an instruction to use more force. Internal faults, wear and alignment errors can all cause resistance. A key that refuses rotation may suggest the cylinder, while handles moving without operating the points can suggest spindle or gearbox trouble. Easy operation while open followed by difficulty when shut can indicate door or keep misalignment. Forcing the key or repeatedly hauling up the handle may increase damage. Separate components can be assessed without assuming the entire assembly needs replacement.
Check What a Cylinder or Label Actually Tells You
A cylinder is generally the key-reading component within a larger system. It passes rotation into the associated mechanism, including recessed mortice cases, nightlatches fitted on the surface and multipoint gearboxes. Renewal can change which keys provide access and may improve protection against some attacks. However, it leaves loose handles, damaged strips, worn gearboxes and door alignment faults untouched. If symptoms remain afterwards, the lock case, spindle, keeps and other connected parts still need consideration.
Euro cylinders have a narrow profile with a rounded upper part. They are familiar on composite, uPVC and aluminium doors and appear on some timber doors too. Single cylinders use a key on one side only. Double cylinders accept keys on each side. Thumbturn versions have an internal knob and an external keyed face. Usually a retaining screw entered from the door edge secures the cylinder through the door and gearbox. The correct length depends on the thickness of both door and handles; excessive projection beyond the outer handle may increase exposure to physical attack.
Oval cylinders provide comparable operation in a rounded oval body. Existing doors and older systems retain them, although newer domestic installations use them less frequently. Matching length cannot make an oval profile fit a euro opening, or vice versa. The furniture and lock case both need to suit the cylinder's shape. Confirm total length, profile, fixing point and the operation required on either face before selecting a part. Unreliable locking, stiffness and odd handle movement also warrant checks of the wider mechanism. Security varies substantially between products, so compare tested performance and resistance to drilling, picking, snapping and other attacks if upgrading protection is the purpose.
A product name can combine mechanism type, case depth, lever count, finish and security standard. Each describes a separate feature.
| Specification term | Interpretation |
|---|---|
| Mortice / rim | Recessed within the edge / mounted on the door surface |
| Deadlock / sashlock | Bolt without a spring latch / deadbolt accompanied by a handle-operated latch |
| Nightlatch | Surface-mounted lock that usually catches as the door shuts |
| Cylinder / multipoint | Key-operated component / connected securing mechanism extending along the edge |
| Case size | Full depth of the mortice body, often expressed using millimetres or inches |
| Backset | Distance from the faceplate edge to the relevant keyhole, cylinder or spindle centre |
| Finish | Visible treatment or colour, such as brass, chrome or satin nickel |
These details narrow the lock family and dimensions. They cannot establish fit when keyhole positions, spindle centres, faceplates or fixing points differ.
A mortice lever lock releases its bolt after the key raises its levers to specified heights. The labels three-lever and five-lever count those internal parts. A five-lever mortice sashlock combines five levers with a latch and deadbolt inside an edge-recessed case. Three-lever units often appear on internal doors or where a higher-security entrance lock is unnecessary. Five-lever units commonly serve external timber doors. Identical lever counts can still conceal different materials, construction, bolt designs and tested resistance, so neither entrance suitability nor insurance acceptance follows from the count.
The presence of five levers does not verify conformity with BS 3621. A performance standard, BS 3621 concerns mechanically operated, thief-resistant single-point assemblies requiring keys on both faces to secure and release them. The tested assembly determines conformity, rather than the lever count. BS 3621:2017+A1:2024 is the current version. Compliant locks normally show a reference on the product or packaging, often together with a certification mark. Older examples may reference a previous edition; inspect the whole marking and identify the precise model. Brand familiarity and bolt length are insufficient evidence. If internal opening is keyless, a different standard may apply because key-operated escape is the scope of BS 3621.
A Lock's Name: How to Read It
Decoding a Product Name
Every lock name packs several facts into one line, usually in the same order. Here is a generic one, read left to right:
- [Maker] — who made it
- five-lever — the number of levers inside
- mortice — the case is recessed into the door edge
- sashlock — a handle-operated latch and a deadbolt together
Mechanism, levers, case size, finish and standard all describe different things, which is why recognising one word never confirms the whole specification. And a five-lever mortice sashlock does not automatically meet BS 3621; that has to be stated and marked separately.
What a Lever Count Actually Means
The key in a lever mortice lock lifts internal levers to particular heights before the bolt can travel. Three levers or five, the count describes the mechanism, not a full security assessment. Three-lever locks often turn up on internal doors; five-lever locks are common on external timber doors, but lever count alone should never be used to judge an entrance door or an insurer's conditions. Compliance with a standard belongs to the tested lock, so check the visible marking and the exact model.
Other Words You Will Meet
Rim locks are mounted on the surface, deadlocks have a bolt but no spring latch, and nightlatches are surface-mounted locks that normally latch on closing. A cylinder is the key-operated part that drives the surrounding mechanism; a multipoint is a connected mechanism with locking points along the edge. Case size is the mortice case's overall depth, backset the distance from the faceplate edge to the centre of the keyhole, cylinder or spindle, and finish the surface, such as brass, chrome or satin nickel. These terms narrow the family and size without proving a fit, because keyhole, spindle, faceplate and fixing points can differ.
The Marking on a Faceplate
Identifying marks are usually on parts visible while the door is open. Mortice and multipoint faceplates may carry a stamped name, logo, series or code; cylinder faces may show a logo or security mark near the keyway. Handles on a multipoint can be from a different maker than the lock beneath. Leave the case, gearbox and strip in place rather than removing them to look for numbers, and even with a code in hand, confirm type and measurements before buying.
Types You Are Less Likely to Meet
Some door locks are simply less common, and they usually work alongside a main lock instead of doing its job.
- A door bolt is surface-mounted and moved by hand, giving the door a second fixing point.
- A hinge bolt helps the hinge edge resist being forced.
- A push-button lock is a mechanical digital lock released by a code, with no batteries, wiring or app. Offices, storage rooms, shared areas and some residential side entrances use them. There is a numbered keypad outside and a knob, lever or thumbturn inside, and the correct code frees the handle to drive the latch or case, possibly a separate tubular latch, mortice latch or lock case. The keypad mechanism, spindle, latch, internal case or alignment may explain why entering the correct code has stopped releasing the door.
- A sliding patio door lock sits in the handle assembly or is connected to a mechanism in the vertical edge of the panel. It may use a single hook or bolt, multiple hooks or locking points, a key cylinder, a separate handle and thumbturn, an anti-lift device and keeps on the meeting frame or fixed panel. The handle shape, fixing positions, cylinder profile and edge faceplate are the clues to look at.
- A window lock belongs to its own family, with its own fittings.
Smart locks and other electronic locks, access control and master key suites are left out of this guide, and they are not something we work on. For a quick view of the main types, return to the comparison table above.
Which Door Each Type Belongs On
Door First, Lock Second
Every type in this guide is explained by one rule: the door decides the lock. Read the door and the lock usually follows.
| Door | What it normally carries |
|---|---|
| Timber, external | A mortice lock, often with a nightlatch |
| uPVC or composite | A euro cylinder in a multipoint strip |
| Aluminium or metal | A multipoint or a cylinder-operated lock case |
| Timber, internal | A lighter mortice latch or sashlock |
| Older timber door or outbuilding | Sometimes a surface-mounted rim lock |
Two exceptions break the pattern. Newer timber doors can be built with multipoints, so age often tells you more than material. A flat entrance door onto a shared corridor has its own considerations, since the method of exit is part of what suits it and a lock opening from inside without a key may come under a different standard.
What to Settle Before a Replacement
Identification narrows the problem but does not confirm the faulty part or its replacement, because similar-looking locks differ in size, operation, security specification and compatibility. Ask four questions: what is fitted; what is causing the fault, given that a stiff key or loose handle may come from the cylinder, case, gearbox, spindle or alignment; whether one part or an adjustment would do; and whether the replacement will fit, work reliably and secure that entrance. Broad labels such as "euro cylinder" or "five-lever sashlock" cannot pin down a part. Brand names and anti-snap labels prove no standard, which belongs to a specific product. If lock changes follow lost keys, a move or a break-in, key control and damage matter as well as fit. When in doubt, arrange an inspection before buying; a clear diagnosis can prevent an unnecessary full lock change.
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Door Lock Type Questions
How can I tell what type of door lock I have?
Start by checking the material of the door and then locate the lock, either embedded in the edge or fixed to the surface. Handles, the key opening, the faceplate and the locking-point arrangement help distinguish cylinder, mortice, multipoint and nightlatch designs. If a key works the bolt but handles operate no latch, it is a deadlock. A sashlock also contains a spring latch, so handles usually sit alongside its keyhole.
What type of lock is usually fitted to a uPVC door?
A modern uPVC entrance door will most often have multipoint locking operated by its handles and euro cylinder. For identification, consider all the components involved. The cylinder forms only part of a system that also contains frame keeps, a gearbox, hooks and a locking strip.
How do I know if I have a mortice lock or a nightlatch?
Check where the lock body is fitted: a mortice lock is housed within the door edge, whereas a nightlatch has a visible casing on the inside surface. Timber entrance doors can carry both types. Finding the surface-mounted body therefore does not rule out a separate recessed lock.
Is a euro cylinder the same as a multipoint lock?
No, multipoint locking refers to the edge-running mechanism, while a euro cylinder is its key-operated component. The difference matters when describing replacement work. Swapping a cylinder leaves these parts of the wider arrangement unchanged: its gearbox, handles, locking points and locking strip.
Can I replace the cylinder without replacing the complete door lock?
You may only need a cylinder change if the wider mechanism is working as it should and the parts are compatible. That option often avoids replacing the complete lock. However, fitting a cylinder cannot put right worn handles, a damaged gearbox or an incorrectly aligned door.
Can I identify a door lock from the key alone?
A key can suggest a lock type, but usually cannot identify it fully. The shape and maker's name may hint at a cylinder or mechanism without confirming its exact model, size or security standard. Photograph the door edge and visible markings for stronger clues.
What if there is no brand name visible on the lock?
It may still be identifiable without a maker's name. Photograph the handles and keyhole, plus the door edge and frame keeps, and record every number or symbol even if it seems unrelated to branding. The lock's dimensions, shape, operation and locking-point layout offer further identification clues.
Does a five-lever lock automatically meet BS 3621?
Having five levers does not make a lock automatically compliant with BS 3621; that describes its internal mechanism. Long bolts and familiar brands are not proof either: compliance concerns the tested assembly. A compliant product will usually carry a BS 3621 reference on its packaging or body, often beside a certification mark. Compare original paperwork with the model, complete visible marking and relevant certification on the lock. Older locks may identify previous editions; BS 3621:2017+A1:2024 is current. This performance standard covers thief-resistant mechanical single-point assemblies keyed for locking and unlocking on each side. Since BS 3621 requires keyed egress, another standard may apply to keyless inside opening.
How can I tell whether my door has a deadlock or a sashlock?
Look for a spring latch alongside the deadbolt: that combination identifies a sashlock, usually accompanied by handles and a keyhole. A deadlock instead has a key-operated bolt without a latch controlled by handles. Begin the broader identification with the door's material, followed by edge-recessed or surface fitting. Compare faceplate, keyhole, handles and number of locking points to separate cylinder, multipoint, mortice and nightlatch types.
Why does my lock work when the door is open but not when it is closed?
The difference between open and closed operation often suggests that locking parts are missing their frame keeps. This can involve the bolt, latch or multipoint locking points. Check alignment, worn hinges and any door movement before reaching a decision about replacing the lock.
Can a locksmith identify my lock from photographs?
Photos can give a locksmith a useful starting identification: often the general type, and possibly a narrower choice of manufacturer or model. For an exact compatibility check, further measurements or an inspection may be required, especially with a multipoint gearbox or mortice case.
What should I do if the door is locked and I cannot identify the lock?
Put attempts involving drilling or prising on hold, and do not keep applying force to the key or handle. The door is locked and the fitting is unidentified, so ask a qualified locksmith to identify it and advise before any further opening attempt.