Guide
Types of Door Locks in the UK: What Each One Is and Where It Fits
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All UK Door Lock Types at a Glance
Most lock names come from one of two places: the complete mechanism, or the single component the key fits into. Mixing those two habits is how mortice lock, nightlatch, euro cylinder and multipoint lock end up being used as if they meant the same thing, when in fact each refers to a different part or system.
That matters the moment something goes wrong, because one of the earliest questions in any repair or replacement is what type of lock you have. The keyhole alone seldom answers it. The door does a better job: note what it is made from, where the mechanism is positioned, and what you can see on its inside face and along its edge. A mortice lock, a nightlatch, a rim cylinder and a multipoint locking system can be told apart using those observations. The main UK types are compared below.
| Family | Where it usually appears | Tell-tale sign | Defining feature |
|---|---|---|---|
| Mortice sashlock | Timber doors, entrance and internal | A recessed case in the edge with a spring latch and a locking bolt | It joins a latch worked by handles to a separate key-operated lock |
| Nightlatch with rim cylinder | Timber entrance doors in most cases | A box-shaped body on the inside face, and its cylinder visible outside | The latch will usually catch when the door closes |
| Mortice deadlock | Timber entrance doors in most cases | A recessed case in the edge, its bolt visible when the door stands open | A key-worked bolt and no handle-worked latch inside the same case |
| Surface-mounted rim lock | Some older timber doors, internal doors and outbuildings | The entire case is fixed where you can see it on the inside face | Surface-mounted rather than housed in the door edge |
| Euro cylinder in a single-point lock | Some timber, aluminium and metal doors | A euro-profile keyway, but no long strip or multiple locking points | The cylinder works a single central lock case |
| Euro cylinder in a multipoint lock | uPVC and composite doors, commonly | A euro-profile cylinder close to the handle, and a long strip on the edge | The cylinder accepts the key, and the wider mechanism controls several points |
These rows point to a general family and never to a precise model. Material is not decisive either: a modern timber door can use a multipoint, while aluminium and metal doors may have cylinder-operated lock cases. Choosing replacement parts requires product markings and measurements first. Further down, this guide explains each common UK type, how to identify it and what its components do, shows where to look for markings, and explains why appearance alone cannot settle the model or security standard. The middle columns are the ones most often misread, so each has its own section next.
Locks Fitted Into a Timber Door
A timber door usually carries one of two things: a lock buried in its edge, or a latch fixed to its inside face, and very often both. If the keyhole is in the edge of the door, you are looking at a mortice lock. If the key passes through the face into a box on the inside, it is a nightlatch. A surface-mounted rim lock is also possible, so the simplest test is whether the case sits inside the edge or can be seen on the inside face.
Mortice Deadlocks and Mortice Sashlocks
A mortice lock sits in a pocket cut into the edge. The deadlock version throws a bolt with the key and nothing else. The sashlock adds a spring latch worked by handles.
Nightlatches and Rim Cylinders
A nightlatch is the box on the inside face, turned from outside by a rim cylinder, and it normally latches as the door closes. An older surface-mounted rim lock looks similar but is not necessarily a nightlatch. Depending on its design, the case may hold a latch, a bolt or both, it may not latch by itself, and it may be worked by a key, a handle or a knob.
When a Door Has Both
Plenty of timber entrance doors carry a nightlatch and a separate mortice lock, working independently, so identify each on its own. Neither is better than the other; they do different jobs. Some timber doors also use a multipoint, a connected system more often seen on uPVC and composite doors, whose locking points move from the edge into frame keeps.
A Lock's Name: How to Read It
Left to Right
A lock name is a chain of facts in roughly fixed order. Decode a generic example:
| [Maker] | five-lever | mortice | sashlock |
|---|---|---|---|
| who made it | levers inside | recessed into the door edge | latch plus deadbolt |
A listing may also carry case size, finish and a security standard, and every one of those terms describes something different, so recognising one does not confirm the whole lock. The five-lever description in the example shown above does not, by itself, prove that the lock meets BS 3621.
What a Lever Count Actually Means
The key in a lever mortice lock lifts internal levers to specific heights so that the bolt can move. Three-lever locks hold three levers and five-lever locks five. That number describes the internals, not the security, since locks sharing a count can still differ in materials, construction, bolt design, resistance to attack and tested performance. Three-lever locks are often found on internal doors or where an entrance-grade lock is not needed; five-lever locks are common on external timber doors. Neither count is enough to confirm suitability for an entrance door or an insurer.
The Vocabulary
Mortice cases are recessed into the edge and rim bodies are surface-mounted. Deadlocks have a bolt with no spring latch; sashlocks pair a deadbolt with a handle-worked latch; nightlatches are surface-mounted and usually latch on closing. The cylinder is the key-operated part that activates the mechanism, and a multipoint places locking points along the edge. Case size is the mortice case's overall depth, backset the distance from faceplate edge to keyhole, cylinder or spindle centre, and finish the visible surface such as brass, chrome or satin nickel. Keyhole, spindle, faceplate and fixing positions can still differ, so these terms do not guarantee a fit.
The Marking on a Faceplate
The best marks are usually on parts visible with the door open, such as a stamped name, logo, series or code on a mortice or multipoint faceplate. A brand helps, but the exact model may need a code, measurements and photographs. Different manufacturers may produce the cylinder, handles and mechanism fitted to a multipoint door. Leave the lock assembled, and confirm type and measurements before ordering. For more on cylinder names, see why anti-snap cylinders are named the way they are.
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.
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 Type Belongs on Each Door
It is the door that decides which lock it carries, never the reverse.
The Exceptions
Timber doors are made with multipoints these days, so how old the door is says more than what it is made from. A flat entrance door onto a shared corridor is the other: how people leave matters, and if the lock can be opened from inside without a key, a different standard may apply.
From Type to Decision
Naming a lock family narrows the problem down, but it does not confirm the faulty part or the right replacement. A recognisable euro cylinder, for instance, may not be the reason a handle will not lift or hooks fail to engage. If the door is already open and the mechanism moves without force, compare how it works open and closed: fine when open but stiff when closed points to alignment and the frame, while a fault that stays with the door open points to the lock or its hardware. Before ordering, answer four questions: what is fitted, why it has failed, whether replacing the whole system is necessary, and whether the new part will fit, operate reliably and secure the entrance properly. Descriptions like "euro cylinder" or "five-lever sashlock" are too broad for an exact part, and brand names or labels prove no standard, which applies to a specific product and model. Similar-looking locks differ in size, operation and compatibility, so if the part or cause is uncertain, get an inspection before buying; it can prevent an unnecessary full lock change.
- Timber external doors: normally a mortice lock, often with a nightlatch.
- uPVC and composite doors: normally a euro cylinder in a multipoint strip.
- Aluminium doors: normally a multipoint or a cylinder-operated case.
- Internal timber doors: usually a lighter mortice latch, sashlock or three-lever lock.
- Older timber doors and outbuildings: sometimes a surface-mounted rim lock.
Not Sure What Lock You Have? Ask Us
If you have reached the end of this guide and the lock is still a mystery, ask. We will tell you what it is, what repairing or replacing it would take, and the price, before anything is touched.
Have to hand: the door material, where on the door the keyhole sits, and a photo of the faceplate along the open edge. If the entrance cannot be secured at the moment, mention that first.
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Door Lock Type Questions
How can I tell what type of door lock I have?
Work from the door material to the mounting position: a lock can sit within the door edge or against its surface. To distinguish mortice, cylinder, nightlatch and multipoint arrangements, inspect handles, keyhole shape, faceplate details and the number of places that lock. A deadlock contains a bolt operated with a key and lacks a handle-operated latch. Sashlocks have a spring latch plus a deadbolt, which explains their usual combination of handles and a 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?
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?
The distinction is between a component and a mechanism: the key operates a euro cylinder, whereas multipoint locking extends along the edge. Installing a replacement cylinder changes only that item. Neither the handles nor the gearbox, locking strip or locking points are replaced by that work.
Can I replace the cylinder without replacing the complete door lock?
A separate cylinder replacement can often be made when the surrounding system is compatible and functioning correctly. It is not a cure for every locking problem. Damage to the gearbox, worn handle components and incorrect door alignment remain problems even after a cylinder has been changed.
Can I identify a door lock from the key alone?
The key rarely identifies the whole lock by itself. A recognisable shape or brand might narrow the cylinder or mechanism, without establishing the exact model, dimensions or security standard. To gather better clues, take photographs of the door's edge and any markings in view.
What if there is no brand name visible on the lock?
Physical features can still help identify a lock with no readable maker's name. Record its dimensions, form, operation and locking-point layout. For photographs, include the handles, door edge, keyhole and frame keeps; also note every symbol and number, including marks that seem unrelated to a manufacturer.
Does a five-lever lock automatically meet BS 3621?
No: describing a lock as five-lever does not confirm compliance with BS 3621. This is a performance standard covering tested, thief-resistant, mechanically operated single-point assemblies, with keys required to lock and unlock both sides. Keyless inside opening may fall under another standard; BS 3621 addresses key-operated exit. Assess the assembly, rather than lever count, bolt length or a known brand. BS 3621:2017+A1:2024 provides the current reference; older locks may cite previous editions. Confirm the visible reference in full, the precise model and relevant certification using original paperwork. Compliance normally brings a BS 3621 reference on the packaging or lock, often beside a certification mark.
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?
Incorrect engagement with the frame keeps is a common explanation: the latch, bolt or multipoint locking points may not line up when closed. Check for worn hinges, poor alignment and movement of the door before treating the lock itself as the part that needs replacement.
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?
Ask a qualified locksmith to identify the unknown fitting and advise on proceeding with the locked door. While identification remains unresolved, do not drill or prise at the lock. Repeated attempts to force either its key or handle should stop at this point.