Guide
Types of Door Locks in the UK: What Each One Is and Where It Fits
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Almost every home in the UK relies on one or more of four lock families, and the door decided which one you have long before you did. They are the mortice lock, set into the edge of the door; the nightlatch, worked from outside by a rim cylinder; the euro cylinder driving a multipoint strip; and the humble surface bolt that adds a second fixing point.
This guide from Woking Locksmith, written for Woking householders and landlords, explains how to recognise each one and how to decode a product listing. It names types; it does not recommend products, quote prices or tell you what to buy.
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Every UK Door Lock Type at a Glance
A locksmith's first question is usually what is fitted, and the keyhole alone rarely settles it. Start with the door instead: its material, where the mechanism sits, and what shows on the inside face and edge. The table below covers every lock type you are likely to meet on a UK domestic door, and the quickest way in is the middle column.
| Lock type | Door it is normally found on | How you recognise it by eye | What a listing usually calls it | Does a British Standard commonly apply? |
|---|---|---|---|---|
| Mortice deadlock | Timber external doors | One keyhole in the face, a bolt in the door edge, no handle | "5 lever mortice deadlock" | Often, to the BS 3621 family |
| Mortice sashlock | Timber external and internal doors | Keyhole plus a square spindle hole, with handles on both sides | "mortice sashlock" | Sometimes, on external versions |
| Nightlatch with rim cylinder | Timber external doors, usually alongside a mortice lock | Round keyway outside, a box on the inside face | "nightlatch" or "deadlocking nightlatch" | Sometimes, on deadlocking versions |
| Euro cylinder in a multipoint mechanism | uPVC and composite doors, and some newer timber doors | Narrow keyhole with a rounded top, a long metal strip along the door edge | "multipoint lock" plus a separate "euro cylinder" | Not to BS 3621; cylinders are rated under TS 007 |
| Euro cylinder in a standalone case | Some timber and aluminium doors | Euro-shaped keyhole, a single case in the door edge | "euro mortice sashlock" or "euro deadlock" | Depends on the case |
| Surface-mounted door bolt | Any door, as an extra | A sliding bolt on the inside face | "door bolt" or "tower bolt" | Rarely |
| Push-button mechanical lock | Communal entrances and offices | A keypad of buttons with no electrics | "digital lock" or "push-button lock" | Rarely |
The middle two columns are the ones people most often get wrong, so each has a section of its own below. What the British Standard on door locks covers is explained in what the British Standard on door locks covers, and if you would like a new lock supplied and fitted rather than identified, see having a lock fitted.
Locks Fitted Into a Timber Door
A timber door usually carries either a lock set into its edge or a latch fixed to its inside face, and quite often both on the same door. Orientation settles which: if the keyhole leads to a case buried in the door edge, it is a mortice lock; if the key passes through the face into a box on the inside, it is a nightlatch. Neither is better. They do different jobs, and for decades most front doors carried one of each.
Mortice Deadlocks and Mortice Sashlocks
The difference is in what is inside the case. A deadlock has a bolt and nothing more, while a sashlock adds a spring latch, which is why a sashlock also needs handles. Both sit in a pocket cut into the door edge, and with the door open you will normally see a metal faceplate with a bolt, a latch or both showing.
A deadlock is locked and unlocked by key from either side and only holds the door shut when it is locked, so it is usually paired with a separate latch or nightlatch. A sashlock does both jobs in one case: the handles work the latch and the key controls the bolt, which makes it the usual fitting on a door that needs to close on a handle and also lock.
| What you see on the door face | |
|---|---|
| Deadlock | One keyhole and no square hole |
| Sashlock | A keyhole plus a square follower hole for the spindle, above or below it |
The lever count in a product name is the number of levers inside that case, which is explained further down. Measuring a mortice lock before you buy one is covered in measuring a mortice lock before you buy one.
Nightlatches and Rim Cylinders
A nightlatch is the box on the inside of a timber entrance door that latches by itself as the door closes, operated from outside by a rim cylinder. Its spring latch drops into a keep on the frame, so nothing needs to be cut into the door edge. It is made up of:
- The case: the box-shaped mechanism on the inside face, with a knob, handle or other control to release the latch from indoors.
- The spring latch: the frame's keep receives this part when the door closes.
- The rim cylinder: the round keyway on the outside face, linked to the case by a flat tailpiece through the door.
Case and cylinder are often sold separately, so a worn cylinder can be changed without touching the case. A deadlocking nightlatch goes further: it can be locked so the latch cannot be slipped, and some versions add a key-locking handle on the inside. If yours has stopped behaving, see a latch or lock that has stopped working properly. A plain nightlatch on its own is not usually what is commonly specified for a final exit door, which is one reason so many timber front doors also carry a mortice deadlock; the guide to BS 3621 and TS 007 explains the standards involved.
There is a third possibility. Screws secure a traditional rim lock to the door's inside face too, although this is a different type of lock from a nightlatch. Its case might hold a latch, a bolt or both, it may not latch by itself when the door closes, and it may be worked by a key, a handle or a knob.
Multipoint Locks Are Not One Type
On a uPVC or composite door, the lock is a strip running most of the height of the door edge, and strips from different makers are not interchangeable. Keep two parts separate: the euro cylinder is what the key turns, and the multipoint is the strip the handle drives. When people ask about uPVC door lock types, they nearly always mean the strip.
What the Strip Itself Tells You
The answer is usually stamped on the metal strip in the door edge, which you can see with the door open. Look for:
- The maker's name. Common UK names include GU Ferco, Avocet, Mila, ERA and Fullex. They are listed here only as identification markers, not as recommendations, and the name is the first thing anyone ordering a part will ask for.
- The PZ. The distance from the centre of the spindle to the centre of the keyhole.
- The backset. The distance from the centre of the keyhole to the edge of the strip.
- The spindle type. A split spindle behaves differently from a single one, because it restricts operation from outside.
Those figures identify the pattern of lock. Ordering a replacement needs the complete set, as explained in changing the cylinder on a uPVC or composite door.
The Locking Points, and Why They Differ
The lumps along the strip are the locking points, and their shape is part of what identifies the lock:
- Rollers pull the door in against its seal.
- Mushroom rollers do the same while also resisting the door being levered.
- Deadbolts throw straight out into the frame.
- Hooks, in small and full sizes, bite into the keep so the door cannot be pushed sideways.
The mix matters. A strip with hooks and mushroom rollers is doing more work than one with plain rollers, and that is the practical difference between two doors that look identical from the street. When the handle lifts but nothing engages, the fault usually lies in the gearbox driving these points rather than in the points themselves; our uPVC door lock service deals with that.
Turning the key operates the cylinder, which usually forms just one component of the complete lock. It reads the key and passes the movement on to whatever surrounds it, which could be a multipoint gearbox, a mortice case or a surface nightlatch. Changing it can alter which keys work the door and may improve resistance to some kinds of attack, but it will not fix a worn gearbox, a damaged strip, a loose handle or a badly aligned door. A euro cylinder has a slim profile with a rounded top section, is common on uPVC, composite and aluminium doors, and also turns up on some timber doors.
Two standards points are worth knowing here. BS 3621 is a performance standard for thief-resistant, mechanically operated single-point lock assemblies that need a key to lock and unlock from both sides, so a multipoint strip is not what it describes. The current version is BS 3621:2017+A1:2024. If a lock can be opened from inside without a key, a different standard may apply, because BS 3621 specifically covers key-operated egress.
This section is about identifying a multipoint, not ordering one. Ordering a replacement needs a full set of measurements, covered in our cylinder-change guide.
How to Read a Lock's Name
A lock's name is four or five facts in a row, nearly always in the same order. Take a generic example: "Maker 5 Lever Mortice Deadlock BS 3621". Read left to right, that is the maker, then the number of levers, then where it fits (mortice, so inside the door edge), then what it does (deadlock, so a bolt only), then the standard it has been tested to. Cylinder listings follow a similar pattern, explained in why anti-snap cylinders are named the way they are.
Lever Counts and What They Actually Mean
The number before the word "lever" is how many levers sit inside the case, and more levers allow more possible key combinations.
| Usual use | |
|---|---|
| 3 lever | Internal doors and lighter duty; not approved to BS 3621 |
| 5 lever | External doors; versions often carry the BS 3621 designation |
The caveat retailer pages tend to skip: a five-lever lock does not automatically comply with BS 3621, because the standard covers much more than how many levers there are. Treat the number and the standard as two separate facts on the listing and check each one. If the lock is already giving trouble, deciding whether a lock needs repairing or replacing is the next read.
The Marking on the Faceplate
The evidence lives on the faceplate, the metal strip visible in the door edge when the door is open. What you may find stamped there:
- a British Standard kitemark and a number beginning BS 3621, on a lock tested to that standard;
- the maker's name, and sometimes the lever count;
- on uPVC strips, the maker and the pattern.
Open the door and look before trusting a listing or a quote, since the faceplate is the one place the lock describes itself. What the standard tests, and what it means for cover, is a topic of its own.
The most useful identifying marks are generally on the parts you can see with the door open. To identify the exact model, you may need a code, measurements and photographs showing the entire mechanism; knowing the maker gives you a starting point. Without dismantling anything, check:
- the faceplate on the door edge, where mortice and multipoint locks may carry a name, logo, series or code;
- the inside case of a nightlatch or rim lock, which may show the brand or model;
- the face of the cylinder, where euro, oval and rim cylinders may have a logo or security marking beside the keyway.
Which Type Belongs on Which Door
The rule behind everything on this page is that the door decides the lock, not the other way round.
Timber external door
normally a mortice lock, often with a nightlatch as well.
uPVC or composite door
normally a euro cylinder in a multipoint strip.
Aluminium door
normally a multipoint or a narrow-stile case.
Internal timber door
a lighter mortice latch or sashlock, or a bathroom lock with a thumbturn.
Two exceptions are worth naming:
- timber doors are now built with multipoints too, so a door's age can tell you more than its material;
- a flat entrance door opening onto a shared corridor has its own requirement, because it must open from inside without a key.
Knowing the family narrows a problem without naming the failed part. Similar-looking locks can differ in size, operation, specification and compatibility, and a whole system may not need replacing when the fault is one compatible part or a door adjustment.
Types You Will Meet Less Often
A few more types appear on UK doors, usually beside a main lock rather than instead of one:
Surface-mounted door bolts
manual, adding a second fixing point.
Hinge bolts
resisting attempts to force the hinge side.
Mechanical push-button locks
common on communal and office doors.
Electronic and smart locks, access control and master key suites are outside the scope of this guide. For a quick summary of everything else, go back to the matrix at the top.
Contact a locksmith even if you have yet to identify the exact model. A clear description usually helps more than a guessed name: say what the door is made of, whether it is open, closed or locked shut, what lock you can see (a mortice keyhole, a nightlatch, a euro cylinder or a long strip), and what happens when you use the key or handle.
Not Sure What You Have? Ask Us
We identify what is fitted, explain what it would take to repair or change it, and give you a price before anything starts. Have ready the door material, where the keyhole sits, and a photo of the faceplate with the door open.
There is no call-out charge, and emergency calls are taken 24 hours a day, every day of the year. [PROVIDER PACK: DBS checks for technicians] [PROVIDER PACK: public liability insurance details]. You get a price on the call from what you describe.
Ask What Lock You Have: call 01483 377197
Door Lock Type Questions
How can I tell what type of lock is on my door?
Look at three things: what the door is made of, where the mechanism sits, and what shows along the edge. Timber doors commonly have mortice locks, nightlatches or rim locks, while uPVC and composite doors often pair a cylinder with a multipoint, although material alone does not prove which you have. A case set into the edge suggests a mortice lock; a box on the inside face points to a nightlatch or rim lock.
What is the difference between a deadlock and a sashlock?
A deadlock has a key-operated bolt and no handle-worked latch. With a sashlock, handles operate the spring latch and a key controls the bolt; the door therefore usually has both handles and a keyhole.
Does a 5 lever lock mean it meets BS 3621?
No. Five lever describes the mechanism inside, and on its own it does not show compliance with BS 3621. Check the lock or its original paperwork for the full standard reference and a certification mark.
What lock does a uPVC door have?
On most modern uPVC entrance doors, the handles and euro cylinder operate a mechanism that locks at multiple points. The cylinder is just one part of that system; the gearbox, strip, hooks and keeps make up the rest.
Can a door have more than one type of lock?
Yes. A timber front door often carries a mortice lock and a nightlatch together, so finding one does not mean there is not another.
Why does my door only lock when I push or lift it?
That usually suggests the latch, bolt or locking points are not meeting the keeps on the frame properly. Before deciding to replace the lock, check whether the door has moved, the hinges are worn or the door is out of alignment. The lock family can often be recognised from photos, which may also offer clues to the maker or model.