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
Start With the Door, Not the Keyhole
A keyhole tells you surprisingly little. When a lock needs fixing or changing, the question that tends to come first is what kind of lock it is, and the door gives a far more dependable answer: check the material, find where the mechanism sits, then look at the inside face and the edge. Between them, those details help tell a mortice lock apart from a nightlatch, a rim cylinder or a multipoint locking system.
| Type | Typical door | Visual clue | Main difference |
|---|---|---|---|
| Nightlatch with rim cylinder | Timber entrance doors, for the most part | A boxy case on the inside face and a separate cylinder visible from outside | It normally latches by itself when the door closes |
| Mortice deadlock | Timber entrance doors, for the most part | A case recessed into the edge, with a bolt you can see once the door is open | Key-operated bolt only, with no latch worked by a handle |
| Mortice sashlock | Timber front, back and internal doors | A recessed case with a spring latch and a locking bolt both visible | Pairs a handle-operated latch with a separate locking action |
| Euro cylinder with a multipoint lock | Commonly uPVC and composite doors | A euro-profile cylinder near the handle plus a long locking strip on the edge | The cylinder takes the key and the mechanism behind it controls several locking points |
| Euro cylinder with a single-point lock | Some timber, aluminium and metal doors | A euro-profile keyway but no long strip or row of locking points | One central lock case, worked by the cylinder |
| Surface-mounted rim lock | Some older timber doors, internal doors and outbuildings | You can see the entire case on the inside face | Mounted on the face of the door, not recessed into its edge |
Why the Names Overlap
Lock names follow one of two habits: they describe either the whole mechanism or just the component that receives the key. That explains why terms like mortice lock, nightlatch, euro cylinder and multipoint lock are so often swapped around, although they refer to different parts or systems.
Treat the table as a guide to the family, never to the exact model. Material is only a pointer, because a modern timber door can be built with a multipoint and aluminium or metal doors may run on cylinder-operated lock cases. Before ordering parts, you still need the product markings and measurements. This guide goes on to explain the common UK types, how to spot them, what their main parts do and where to find markings, along with why appearance cannot confirm a model or security standard. The middle two columns cause the most mistakes, so both get a section of their own.
Timber Doors and the Locks Fitted Into Them
Edge or Face?
A key that enters the edge of the door operates a mortice lock; a key that passes through the face into a box on the inside operates a nightlatch. Often a door has both. Mortice locks, nightlatches, surface-mounted rim locks or two separate systems combined are all common, and where the case sits, inside the edge or on the inside face, is the easiest way to sort them.
Mortice Sashlocks and Mortice Deadlocks
Mortice locks are cut into the door so that only a faceplate shows on the edge. A mortice deadlock has a bolt that only the key moves. A mortice sashlock also has a spring latch operated by the handles.
Nightlatches and Rim Cylinders
A nightlatch is a box on the inside face, operated from outside through a rim cylinder, and it usually catches as the door shuts. The inner face of a timber door is also where a traditional rim lock is mounted, although this does not necessarily make it a nightlatch. Some designs contain a latch, some a bolt and some both. Unlike a typical nightlatch, it may not latch automatically, and a key, handle or knob may operate it.
A nightlatch and a separate mortice lock are sometimes used together on timber entrance doors. With this arrangement, each lock operates separately and should be identified on its own. They do different jobs, and neither is the better lock. Some timber doors also carry a multipoint, a complete system of connected parts that is common on uPVC and composite doors, with locking points along the edge moving into keeps on the frame.
Multipoint Locks Are Not a Single Type
The lock on a uPVC or composite door includes a strip extending along the height of its edge; different makes cannot be treated as interchangeable. The key rotates the euro cylinder, while the handle drives the multipoint mechanism through its gearbox. Most questions about uPVC lock types concern this door strip. Identifying its maker, layout and locking points matters whenever replacement parts are considered.
What You Can Tell From the Strip Itself
Multipoints also appear on some aluminium and timber doors. Their connected locking points engage metal keeps attached to the frame. With the door securely open, look for hooks, pins, bolts or rollers distributed above and below the central mechanism.
| Component | Function within the assembly |
|---|---|
| Euro cylinder | Recognises the key and transmits its rotation to the mechanism |
| Handle set and spindle | Carry movement across the door and into the gearbox |
| Central gearbox | Receives the handle and cylinder inputs and operates the connected points |
| Faceplate and door strip | Run along the edge and connect the central mechanism with the other locking positions |
| Hooks, pins, rollers and bolts | Enter corresponding frame fittings; a strip can combine different types |
| Frame keeps | Receive the latch and projecting locking parts |
Record the maker's lettering, any logo or code, and markings beside the latch. Count the locking points and note their form, spacing and relationship to the gearbox. Photographs should cover the full edge, both handles, the cylinder and readable stamps.
Two identification dimensions often appear in descriptions: PZ, measured between the spindle centre and cylinder centre, and backset, measured between the faceplate edge and cylinder centre. Matching these alone cannot establish compatibility. Faceplate details, gearbox connections and the positions of individual locking points can still differ. Ordering requires proper measurements; the separate cylinder replacement guide covers that stage.
Many mechanisms engage their points when the handle rises, after which the key prevents handle release. Other designs secure themselves as the door shuts or move their points through key operation. None of these operating patterns identifies an exact model by itself.
Resistance deserves investigation, not extra force. An unresponsive key may implicate the cylinder, while freely moving handles with stationary locking points suggest a spindle or gearbox issue. Difficulty only when the door is shut can indicate alignment trouble involving the door or keeps. Wear and internal damage can also create stiffness. Repeated pressure on the handle or key may worsen it, and replacing every component is not automatically necessary.
Separate the Cylinder, Description and Standard
The cylinder usually forms only the keyed element of a larger lock. Its movement can operate a nightlatch mounted on the door surface, a mortice case or the gearbox of a multipoint. Changing it can provide different working keys and may improve resistance to particular attacks. It cannot restore a worn gearbox, straighten a damaged strip, tighten loose handles or correct alignment. Persistent symptoms can still involve the spindle, lock case or keeps as well as those parts.
A euro cylinder has a slim outline topped by a rounded section. It is common on aluminium, uPVC and composite doors, with some timber installations too. Single versions take a key on one face; double versions use keys on either face; thumbturn versions pair an external key with an internal knob. The cylinder extends through the gearbox and door, normally secured by an edge-mounted retaining screw. Its length must match the combined door and handle thickness. Excess projection outside the handle may leave it more vulnerable to physical attack.
Oval cylinders serve much the same purpose but have an oval outline. They remain in older systems and existing doors, although newer domestic fittings use them less often. Similar lengths do not make oval and euro profiles compatible: both the furniture aperture and lock case must accept the chosen shape. Confirm profile, total length, fixing location and the operating arrangement on each face. Investigate the connected mechanism if locking is inconsistent, the handle behaves oddly or operation feels stiff.
Security differs between cylinder products. Check tested performance and resistance to drilling, snapping, picking and other attacks when protection motivates the change; appearance alone says little.
Lock descriptions combine separate specifications. Mechanism, lever count, case dimensions, finish and security standard each answer a different question.
| Description | What it establishes |
|---|---|
| Mortice or rim | A case recessed into the door edge, or a body fitted on the door surface |
| Deadlock or sashlock | A bolt without a spring latch, or a deadbolt combined with a handle-operated latch |
| Nightlatch | A surface-fitted lock that normally catches when the door shuts |
| Cylinder or multipoint | The keyed component, or a connected mechanism securing several positions along the edge |
| Case size | The total depth of the mortice case, commonly expressed in inches or millimetres |
| Backset | The distance between the faceplate edge and the centre of the relevant keyhole, cylinder or spindle |
| Finish | The visible treatment or colour, including brass, satin nickel or chrome |
These labels narrow the options without guaranteeing fit. Keyhole position, spindle location, fixings and faceplate can vary. A five-lever mortice sashlock, for example, sits within the door and combines a latch, deadbolt and five internal levers. Its key raises those levers to the required heights before allowing bolt movement. Three-lever versions contain three levers instead. Three-lever locks often serve internal doors; five-lever locks commonly appear on external timber doors. Neither count settles entrance suitability or an insurer's requirements. Construction, materials, bolt design and tested attack resistance still matter.
Having five levers does not establish compliance with BS 3621. This performance standard addresses mechanically operated, thief-resistant single-point assemblies needing a key on either side for both securing and releasing the lock. Compliance belongs to the tested assembly. BS 3621:2017+A1:2024 is the current edition. Compliant products normally reference BS 3621 on their packaging or on the lock, frequently with a certification mark. Earlier editions may appear on older examples, so examine the complete marking and precise model. A familiar maker or lengthy bolt proves nothing by itself. Where internal opening needs no key, another standard may be relevant because BS 3621 concerns key-operated exit.
Which Type Belongs on Which Door
The door decides the lock, not the other way round. Start with the door and the likely family follows:
Timber front or back door
normally a mortice lock, often with a nightlatch as well.
uPVC or composite door
normally a euro cylinder driving a multipoint strip.
Aluminium or metal door
usually a multipoint or a cylinder-operated lock case.
Internal timber door
often a mortice sashlock or lighter three-lever lock.
Older timber door or outbuilding
sometimes a surface-mounted rim lock.
Two exceptions are worth knowing. Timber doors are now made with multipoints too, so material alone does not settle it. And a flat entrance door onto a shared corridor is a case of its own, because the way people get out matters; where a lock can be opened from inside without a key, a different standard may apply.
Naming It Is Not the Same as Fixing It Knowing the family narrows a problem down without confirming which part has failed or what should replace it. Dimensions, operation, security and compatibility can all differ between locks with the same appearance. Before buying a part or agreeing to a replacement, answer four questions: what is fitted, what is causing the fault, whether the whole system really needs replacing, and whether the replacement will fit, work reliably and suit that entrance. A label such as "euro cylinder" or "five-lever sashlock" is too broad for that, because the right part can depend on measurements, handing, faceplate shape, fixing positions, case size and connected hardware. A familiar brand, a five-lever description or an anti-snap label is not proof of a standard either; certification applies to a specific product, so check the full reference and exact model. If the part or the cause is unclear, have the door inspected first: a clear diagnosis can avoid an unnecessary full lock change.
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.
Types You Are Less Likely to Meet
Beyond the main families, several other types appear on UK doors, and most of them work alongside a primary lock.
Door bolts
surface-mounted and operated manually, add a second point of fixing.
Hinge bolts
protect the hinge side of a door against being forced.
Push-button (mechanical digital) locks
use a code instead of batteries, wiring or an app. You will see them on offices, storage rooms, communal areas and some residential side doors. A numbered keypad sits outside and a knob, lever or thumbturn inside; entering the code releases the handle so it can move the latch or case. A separate tubular latch, mortice latch or lock case may have a connection to the keypad. For identification, take photographs showing the door from both sides, its edge faceplate and any markings on the keypad housing.
Sliding patio door locks
differ from those on hinged entrance doors. They are built into the handle assembly or linked to a mechanism inside the vertical edge of the sliding panel, and may use a single hook or bolt, multiple hooks, a key cylinder, a handle and thumbturn, an anti-lift device and keeps on the meeting frame or fixed panel. Identify one from the handle shape, fixing positions, cylinder profile and faceplate, and record any stamped name or number.
Window locks
form a separate family with dedicated fittings.
This guide does not cover electronic or smart locks, access control or master key suites, and none of those is part of our work. The table at the start of this guide summarises the rest.
Unsure What You Have? Ask Us
Still Not Sure? Ask Us Tell us about the door and we will say what lock is fitted, what it would take to change or repair it, and what that costs before we start.
It helps to know the door material and where the keyhole sits, and to have a photo of the faceplate along the edge while the door is open. If the door cannot currently be locked or secured, say so straight away.
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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?
Most modern uPVC front doors have multipoint locking, controlled through the handles and a euro cylinder. Look beyond the cylinder when identifying the system: the full arrangement also takes in a gearbox, hooks, the locking strip and keeps fitted to the frame.
How do I know if I have a mortice lock or a nightlatch?
Look for an exposed lock case on the inner face to recognise a nightlatch; a mortice lock instead occupies a recess in the door's edge. Do not stop after spotting either type. A timber entrance door may be fitted with both arrangements.
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?
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?
Full identification is usually not possible from just a key. Branding and shape may point to a particular mechanism or cylinder, but the complete model, dimensions and security standard seldom follow from that alone. Clear views of the door edge and visible markings provide better clues.
What if there is no brand name visible on the lock?
Use the lock's physical details if no maker's name is visible: its shape, size, operation and locking-point positions may identify it. Include the door edge, handles, frame keeps and keyhole in photographs. Write down any symbols or numbers rather than dismissing them as unrelated markings.
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?
A bolt operated by a key, without a handle-controlled latch, points to a deadlock. A sashlock includes a sprung latch as well as the deadbolt, normally explaining the presence of handles and a keyhole. First note the door material for broader identification, then check for edge-inset or surface mounting. Study the keyhole, handles and faceplate, and count locking points to distinguish cylinder, mortice, nightlatch and multipoint arrangements.
Why does my lock work when the door is open but not when it is closed?
Often, closing the door reveals an alignment problem: multipoint locking points, a bolt or a latch are missing the frame keeps. The next check should cover movement in the door, hinge wear and poor alignment. Establish those points before assuming the lock has to be replaced.
Can a locksmith identify my lock from photographs?
A locksmith can often identify the general lock category from pictures, with the manufacturer or model sometimes becoming clearer too. Confirming an exact compatible part may take measurements or a direct inspection. That is particularly relevant to multipoint gearboxes and mortice lock cases.
What should I do if the door is locked and I cannot identify the lock?
Stop forcing the key or handle, and avoid drilling or prising at the lock. If the door remains locked and its mechanism is unknown, leave further attempts there. Ask a qualified locksmith to identify the fitting and advise on how to proceed.