Guide
Types of Door Locks in the UK: What Each One Is and Where It Fits
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Every UK Door Lock Type at a Glance
One Screen, Six Lock Families
The matrix that follows compares the main lock types found on doors across the UK. Begin with the column describing what you can see, since that is the quickest way to match a row to your own door.
| What it is called | Common door material | What to look for | What makes it distinct |
|---|---|---|---|
| Surface-mounted rim lock | Some older timber doors, internal doors and outbuildings | A lock case visible in full on the inside face of the door | It is mounted on the surface, with nothing recessed into the edge |
| Mortice deadlock | Usually timber entrance doors | A case fitted into the door edge, with a bolt visible when open | A bolt worked by key, without a handle-operated latch in the case |
| Mortice sashlock | Timber entrance doors and internal doors | A case fitted into the edge, showing both a spring latch and a bolt | A latch for the handles plus a separate locking function |
| Nightlatch with rim cylinder | Usually timber entrance doors | A box-like case on the inside face and a separate cylinder outside | Closing the door usually engages the latch |
| Euro cylinder with a multipoint lock | Common on uPVC and composite doors | A euro-profile cylinder near the handle with a long locking strip down the edge | The key goes into the cylinder, but the wider mechanism works several locking points |
| Euro cylinder with a single-point lock | Some timber, aluminium and metal doors | A euro-profile keyway and no long strip or several locking points | A single central lock case is operated by the cylinder |
How to Use It
Whenever a lock has to be repaired or replaced, someone will ask early what type is fitted, and studying the keyhole alone will rarely give the whole answer. The door is the most reliable place to start. Check its material, find where the lock mechanism is, and look at what appears on the inside face and along the edge. Identifying whether it is a mortice lock, a nightlatch, a rim cylinder or a multipoint system is easier with those signs.
Names complicate things. Locks tend to be named after either the whole mechanism or the key-accepting component, so mortice lock, nightlatch, euro cylinder and multipoint lock are confused even though they describe different parts or systems. Each description here identifies a family, not an exact model. Multipoint systems can be fitted to modern timber doors, while cylinder-operated lock cases may be used on aluminium and metal doors. You will still need markings and measurements before choosing parts. The sections below explain the common types, how to recognise them and what the main parts do, show where markings are found, and explain why appearance cannot confirm a model or security standard, starting with the two middle columns people get wrong.
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.
How to Read the Name of a Lock
Once you know the order, a product name stops being jargon. It usually runs maker, lever count, where the lock fits, what it does, and then any finish, case size or standard. So [Maker] five-lever mortice sashlock decodes as a named manufacturer, five internal levers, a case fitted inside the door, and a combined latch and deadbolt. Each element describes a different aspect, so recognising one term does not confirm the full specification, and that five-lever description on its own does not mean the lock meets BS 3621.
What Each Term Means
- Mortice: the case is recessed into the door edge
- Rim: the main body is mounted on the door surface
- Deadlock: a bolt but no spring-operated latch
- Sashlock: a deadbolt combined with a handle-operated latch
- Nightlatch: surface-mounted, normally latching as the door closes
- Cylinder: the key-operated component that activates the mechanism
- Multipoint: a connected mechanism with locking points along the edge
- Case size, backset, finish: the case's overall depth; the distance from faceplate edge to keyhole, cylinder or spindle centre; the visible surface, such as brass, chrome or satin nickel
These narrow the family and dimensions but do not confirm a fit, because keyhole, spindle, faceplate and fixing points may sit differently.
Lever Counts: What They Actually Mean
Before a lever mortice lock's bolt can move, the key must lift its levers to set heights: three in a three-lever lock, five in a five-lever. Three-lever locks often appear on internal doors; five-lever locks are common on external timber doors. Equal counts can hide different materials, construction, bolt design and tested performance, so the count is not a security verdict or a test of what an insurer requires.
The Markings on the Faceplate
Marks are easiest to find on parts visible while the door is open. Mortice and multipoint faceplates may show a maker's name, logo, series or code. Even with a code visible, confirm the lock type and measurements before ordering, because similar components appear across ranges. Do not dismantle a lock case, gearbox or strip to search for a hidden number.
Multipoint Locks: Not One Type
The locking strip on a composite or uPVC door runs the height of its edge, and another make is not automatically a compatible substitute. A euro cylinder turns with the key; a multipoint mechanism moves through the handle and its gearbox. Most attempts to identify a uPVC lock concern the latter. The maker, strip geometry and arrangement of locking points together establish what needs identifying.
What the Strip Itself Can Tell You
An open door reveals the parts that make a multipoint different from a single locking position. Hooks, rollers, bolts or pins appear above and below the central latch and gearbox. A mechanism can use a mixture. Matching metal keeps on the frame receive the locking points and latch. The same general lock family also appears on certain aluminium and timber doors.
| Connected element | Purpose |
|---|---|
| Frame keeps | Receive the securing parts and latch when the door is locked |
| Hooks, rollers, pins and bolts | Extend from the edge towards those keeps |
| Long edge strip and faceplate | Connect and cover the mechanism running between locking positions |
| Central gearbox | Controls linked movement after receiving input from the handles or cylinder |
| Handle spindle | Carries handle motion through the door to the gearbox |
| Cylinder | Recognises the key and transmits its rotation into the lock |
For identification, make a record of the point count, point shapes and spacing, plus the gearbox location. Inspect the faceplate for names, logos and stamped references. Look beside the latch for further labels. Photographs should show the complete edge and close views of the handles, cylinder and all legible markings.
Measure nothing for ordering from a name alone. PZ identifies the gap between the centres of the cylinder and handle spindle. Backset identifies how far the cylinder centre lies inward of the faceplate edge. These are clues, not a complete specification: strips sharing both can differ in their gearbox connections, faceplate or securing-point locations. Ordering replacement parts needs proper measurements, dealt with in the separate guide on cylinder replacement.
With many handle-operated strips, lifting the handle engages the points and turning the key prevents the handle withdrawing them. Other systems engage as the door closes, while some use key rotation to move the points themselves. Operating style helps describe the mechanism but cannot confirm a specific manufacturer or model.
Watch how a fault changes with the door open. Binding only after closure may suggest that the door or frame keeps are misaligned. A handle travelling without driving the points can indicate spindle or gearbox trouble. Failure of the key to rotate can involve the cylinder. These symptoms are clues rather than certain diagnoses. Internal defects and wear can also cause stiffness. Stop forcing the key or lifting the handle against resistance, as further pressure may cause additional damage. Replacing every connected part is not necessarily required.
Separate Cylinder Details from Lock Performance
The cylinder normally supplies key operation to a larger mechanism, which can be a multipoint gearbox, a surface nightlatch or a mortice case. A cylinder change can give the door new working keys and may strengthen protection against certain attacks. It does not cure a worn gearbox, damaged strip, loose handle or badly aligned door. Continued symptoms can still require attention to the case, spindle, handles, keeps and wider mechanism. Knowing the cylinder profile therefore leaves the rest of the door to be assessed.
The familiar euro profile is slender beneath a rounded upper portion. It is common on composite, aluminium and uPVC doors, with some timber installations using it too. A single cylinder is keyed on one side, a double is keyed on both, and a thumbturn has an external key with an internal knob. Normally it passes through the gearbox and door and is retained by an edge screw. Length must suit the combined thickness of handles and door. An outer end protruding excessively beyond the handle may be more exposed to physical attack.
Oval cylinders fulfil a comparable role in a rounded oval shape. They are seen less in newer domestic installations but remain in older systems and existing doors. Euro and oval bodies cannot replace one another simply on the strength of similar lengths. The furniture aperture and surrounding case must accept the required profile. Establish that profile, overall length, fixing position and operating method on each face before choosing a replacement. Stiff operation, unreliable locking and unusual handle movement require checks of the connected mechanism as well.
Security features differ substantially between cylinders. If better protection is the aim, examine tested standards and resistance to drilling, snapping, picking and other attacks instead of relying on the outline.
Product descriptions contain several independent pieces of information. Mechanism type, lever count, case size, surface finish and security standard each describe something different.
| Description element | Meaning |
|---|---|
| Mortice | Case recessed into the door edge |
| Rim | Main body fitted to the surface |
| Deadlock | Bolt provided without a spring-operated latch |
| Sashlock | Deadbolt together with a latch operated through handles |
| Nightlatch | Surface-fitted lock that normally catches on closing |
| Multipoint | Connected mechanism with securing positions distributed along the edge |
| Cylinder | Key-operated part activating the surrounding mechanism |
| Case size | Total mortice case depth, commonly given in inches or millimetres |
| Backset | Distance between faceplate edge and the appropriate cylinder, spindle or keyhole centre |
| Finish | Visible treatment or colour, such as satin nickel, chrome or brass |
These terms help narrow identification and dimensions. They cannot guarantee replacement compatibility where fixing points, keyhole positions, spindle locations or faceplates differ.
Lever locks use the key to raise internal levers to particular heights before releasing bolt movement. A three-lever mechanism contains three levers and a five-lever mechanism contains five. A five-lever mortice sashlock places five levers, a deadbolt and a handle-operated latch within a recessed body. Three-lever locks often serve internal doors or uses without a higher-security entrance requirement. Five-lever locks frequently serve external timber doors. Materials, manufacture, bolt design and tested attack performance can differ despite matching lever counts, so entrance suitability and an insurer's requirements need separate confirmation.
Specifying five levers does not confirm that BS 3621 has been met. BS 3621 is a thief-resistance performance standard covering mechanically operated single-point assemblies requiring keyed locking and unlocking at both faces. Compliance rests on the tested assembly rather than its lever quantity. The current standard designation is BS 3621:2017+A1:2024. Compliant locks normally reference BS 3621 on the hardware or packaging, frequently accompanied by a certification mark. Older examples may cite previous editions; check the complete marking alongside the exact model. Neither a familiar brand nor an extended bolt is proof. A different standard may govern keyless internal opening, because the egress covered by BS 3621 requires a key.
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 Does Each Type Belong On?
Here is the rule behind everything on this page: the door chooses the lock. Working through the common doors in turn:
- A timber external door normally has a mortice lock, often paired with a nightlatch.
- A uPVC or composite door normally has a euro cylinder working a multipoint strip.
- An aluminium door normally has a multipoint or a lock case operated by a cylinder.
- An internal timber door usually has a lighter mortice latch or sashlock.
- Some older timber doors, internal doors and outbuildings carry a surface-mounted rim lock.
The exceptions: multipoints are now fitted in timber doors too, so a door's age matters more than its material alone; and a flat entrance door onto a shared corridor has its own considerations about how people get out, because a lock that opens from inside without a key may come under a different standard.
What Identification Does Not Tell You Recognising a mortice, nightlatch, cylinder or multipoint helps narrow things down but does not show which part is faulty or what should replace it. Locks that look similar can differ in dimensions, operation, security specification and compatibility. Before ordering or agreeing to replacement, settle four questions: what the lock is, what is causing the problem, whether one compatible component or an adjustment would do, and whether the replacement fits, operates reliably and secures that entrance properly. Two mortice cases can fit similar openings yet put the keyhole, spindle or bolt in different places, and altering the door for the wrong lock can weaken it. Brands, five-lever descriptions and anti-snap labels prove no particular standard, since certification applies to a specific product; check the full reference and model. When the cause or the part is uncertain, arrange an inspection before buying, because a clear diagnosis can avoid an unnecessary full lock change.
Unsure What You Have? Ask Us
Ask Us What You Have We identify what is fitted, explain what changing or repairing it would involve, and give you a quote before any work starts. A door that does not fit neatly into this guide is the call most worth making.
To help, have the door material to hand, tell us where the keyhole is, and take a photo of the edge faceplate with the door open.
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Door Lock Type Questions
How can I tell what type of door lock I have?
Take the door's material as the first clue, followed by whether the lock is housed in the edge or secured on a face. The faceplate, keyhole, handles and count of locking points can indicate a multipoint mechanism, cylinder, nightlatch or mortice lock. A deadlock's key operates its bolt, but there is no handle-worked latch. Adding a spring latch to a deadbolt gives a sashlock, generally recognisable by handles as well as the keyhole.
What type of lock is usually fitted to a uPVC door?
Multipoint locking is the common arrangement for modern uPVC entrance doors. The wider assembly includes a locking strip, hooks, gearbox and frame keeps. A euro cylinder operates it together with the handles, so the cylinder is only part of the system being identified.
How do I know if I have a mortice lock or a nightlatch?
A mortice lock sits within the door edge; a nightlatch sits visibly against the inside face. Check both positions when examining a timber entrance door. It may have the two types together, meaning that identifying one fitting does not establish that it is the only lock.
Is a euro cylinder the same as a multipoint lock?
Think of the euro cylinder as one key-operated part, with the multipoint lock forming the mechanism along the door edge. They are not interchangeable descriptions. A new cylinder leaves the locking strip and gearbox as they were, along with the handles and locking points.
Can I replace the cylinder without replacing the complete door lock?
Yes, the whole lock does not always need replacing when a cylinder is changed. The remaining mechanism must work correctly and be compatible with the new part. If the trouble comes from worn handles, door misalignment or a damaged gearbox, a cylinder replacement will not solve it.
Can I identify a door lock from the key alone?
Generally, no: the key gives only part of the picture. Its maker's name or shape can suggest a cylinder or mechanism, but rarely verifies the precise lock model, size or security standard. For identification, photographs of visible markings and the door edge are more useful.
What if there is no brand name visible on the lock?
Look beyond branding to the lock's shape, dimensions, operating method and layout of locking points; these may still establish its identity. Photograph both the handles and keyhole, as well as the door edge and frame keeps. Note symbols and numbers whether or not they seem to identify a maker.
Does a five-lever lock automatically meet BS 3621?
No, lever count does not prove that a lock meets BS 3621. Compliance belongs to the tested assembly, rather than internal lever numbers, bolt length or brand familiarity. For thief-resistant mechanical single-point assemblies, BS 3621 sets performance requirements with keyed locking and unlocking from both sides. Opening inside without a key may bring another standard into play, since BS 3621 covers keyed egress. Older markings may cite predecessors to BS 3621:2017+A1:2024, the current edition. Verify the exact model, full visible reference and relevant certification mark using original documents. Compliant locks normally carry the reference on product or packaging, often alongside certification.
How can I tell whether my door has a deadlock or a sashlock?
Check whether handles work a latch as well as there being a deadbolt. A sashlock combines those features, so handles normally accompany its keyhole; a deadlock uses a keyed bolt and has no handle-driven latch. To identify the wider lock type, start with door material, then its recessed-edge or surface position. Keyhole details, handles, faceplate and locking-point numbers distinguish nightlatch, mortice, cylinder and multipoint systems.
Why does my lock work when the door is open but not when it is closed?
Suspect the fit between the door's locking parts and the frame keeps first. In this situation, a bolt, latch or multipoint locking points often fail to engage correctly. Assess whether movement, poor alignment or worn hinges is involved before concluding that the lock needs replacing.
Can a locksmith identify my lock from photographs?
Photographs often let a locksmith recognise the broad lock type and may help narrow the maker or model. They do not always establish exact compatibility. Measurements or an inspection may still be needed, especially when identifying a mortice case or multipoint gearbox.
What should I do if the door is locked and I cannot identify the lock?
Do not respond to an unknown lock by drilling, prising or forcing the key or handle repeatedly. Pause further work on the locked door and seek a qualified locksmith's help with identification. Ask for advice on proceeding once the fitting has been identified.