Lock knowledge
Types of door locks explained, in plain English.
Euro cylinders, mortice locks, night latches, multi-point mechanisms, anti-snap and smart locks: what each one is and where it belongs.
If you have ever stood in front of your own door not quite sure what is holding it shut, this is the page for you. Which lock you have comes down almost entirely to one thing: whether your door is uPVC, composite or timber. uPVC and composite doors use a euro cylinder driving a multi-point mechanism. Timber doors use mortice locks and night latches. On top of those sit the security upgrades (anti-snap cylinders to TS007 3-star) and the newer smart locks. This guide names every type, explains what it is and where it belongs, tells you which one your insurer actually wants, and shows you how to identify yours in thirty seconds. Written by a working locksmith who fits all of them every week, with no jargon left unexplained.
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UK door lock types at a glance
The quick version. Find your door material in the second column, and the rest follows. The detailed explanation of every type is in the next section.
| Lock type | Door it suits | Security standard | Insurer-approved? |
|---|---|---|---|
| Euro cylinder | uPVC / composite | TS007, Sold Secure SS312 | Yes, if 3-star anti-snap |
| Multi-point mechanism | uPVC / composite | Rated via its cylinder | Via the cylinder fitted |
| 5-lever mortice deadlock | Timber | BS3621 | Yes (classic requirement) |
| Mortice sashlock | Timber | BS3621 (deadbolt) | Yes if BS3621 |
| Night latch (rim cylinder) | Timber front | BS3621 (auto-deadlocking) | Only BS3621 versions |
| Rim deadlock | Older / timber | Varies | Rarely on its own |
| Anti-snap cylinder (TS007 3-star) | uPVC / composite upgrade | TS007 3-star / SS312 Diamond | Yes |
| Smart lock | Various | Check insurer | Check your policy |
Standards in plain English: BS3621 is the British Standard for mortice locks on timber doors; TS007 is the 1, 2 and 3-star anti-snap rating for euro cylinders; Sold Secure (run by the Master Locksmiths Association) grades cylinders up to SS312 Diamond.
The main types of door lock explained
Eight lock types cover almost every UK home. Each entry below is what the lock is, where you will find it, and what it means for security and insurance.
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Euro cylinder
What it is. The removable key barrel found in nearly every uPVC and composite door, shaped like a fat figure-8 if you look at it end-on. It does not lock the door by itself; it drives the multi-point mechanism (number 2). Pull the central fixing screw out of the door edge and the whole cylinder slides out, which is why a cylinder swap is one of the quickest, cheapest lock jobs there is.
Where you'll find it. Almost every uPVC and composite front, back and side door in the UK. If your door is plastic or a composite slab and you lift a handle to lock it, you have one of these.
Security and insurance. The cylinder is the part a burglar attacks, usually by snapping it. A basic cylinder offers little resistance; an anti-snap upgrade to TS007 3-star or Sold Secure SS312 Diamond is what your insurer wants on a uPVC door. Measuring one for replacement catches people out, so there is a dedicated euro cylinder size guide.
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Multi-point locking mechanism
What it is. The long metal strip down the opening edge of a uPVC or composite door that throws several locking points at once, hooks, rollers and deadbolts, top and bottom as well as the centre, when you lift the handle and turn the key. The gearbox in the middle is the working heart of it.
Where you'll find it. Paired with the euro cylinder on uPVC and composite doors. The cylinder is the key part you see; the mechanism is the hidden part that does the actual bolting.
Security and insurance. Mechanically, the gearbox is the bit that wears out: a handle that goes floppy, or lifts but will not lock, is usually a failed gearbox, not a failed cylinder. A like-for-like gearbox swap is from £145, and the door won't lock guide helps you tell a gearbox fault from simple door drop.
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Five-lever mortice deadlock
What it is. A heavy lock body that sits inside a pocket (a "mortice") cut into the edge of a solid timber door, worked by a traditional chunky lever key. It throws a single deadbolt deep into the frame. "Five-lever" refers to the number of levers the key has to lift, and more levers means more key differs and more security.
Where you'll find it. Wooden front and back doors, very often as the lower of two locks (a night latch above, a mortice deadlock below).
Security and insurance. A five-lever mortice deadlock to BS3621 (look for the BSI kitemark stamped on the faceplate) is the classic UK home-insurance requirement for a timber door. Supply and fit is from £120.
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Mortice sashlock
What it is. The same idea as a mortice deadlock, but with a spring latch built in alongside the deadbolt, so a handle can be used to open and close the door in normal use, and the key throws the deadbolt for security. "Sash" here just means it combines latch and bolt in one case.
Where you'll find it. Timber doors where you want handle operation as well as a deadlock, including internal doors and many back doors.
Security and insurance. For insurance on a final-exit timber door, the deadbolt should still meet BS3621. A sashlock that is not kitemarked is fine for an internal door but may not satisfy your policy on an external one.
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Night latch (rim cylinder)
What it is. The lock that bolts onto the inside face of a timber door, with a small round key on the outside and a snib or turn on the inside. The classic "Yale-type" lock. It latches automatically when the door closes. The outside key part is a rim cylinder.
Where you'll find it. The upper lock on traditional wooden front doors, usually paired with a mortice deadlock below.
Security and insurance. A standard night latch can be slipped or is only deadlocked when you double-lock it. An auto-deadlocking night latch to BS3621 is the insurance-grade version. On its own a basic night latch is rarely enough for a policy; insurers usually want the BS3621 mortice as well.
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Rim deadlock and rim lock
What it is. A surface-mounted lock body fixed to the face of the door (rather than morticed into the edge), throwing a deadbolt into a keep on the frame. Older rim locks are often large, traditional cast units; modern rim deadlocks are slimmer.
Where you'll find it. Period properties, outbuildings, and timber doors where cutting a mortice is not practical.
Security and insurance. Security varies enormously by age and quality. A modern rim deadlock can be solid; a very old rim lock is often more about heritage than security. On a final-exit door, insurers usually want a BS3621-rated lock somewhere on the door, so a rim lock alone is rarely sufficient.
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Anti-snap cylinder (TS007 3-star)
What it is. Not a separate door lock so much as the secure upgrade version of the euro cylinder. It is engineered with a sacrificial snap line and hardened internals so that, even if a burglar snaps the front section off, the lock keeps the door secure. Tested to the TS007 Kitemark star rating and Sold Secure grades.
Where you'll find it. Any uPVC or composite door that currently has a basic cylinder. It drops straight into the existing multi-point mechanism.
Security and insurance. The gold standard for uPVC and composite door security and what most insurers now ask for: TS007 3-star, or a 1-star cylinder paired with 2-star security handles, or a Sold Secure SS312 Diamond cylinder. An upgrade typically runs £150 to £250 fitted depending on the cylinder.
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Smart lock
What it is. An electronic lock operated by keypad, app, fob or fingerprint rather than (or as well as) a key. Some replace a whole mechanism; many retrofit onto an existing euro cylinder or night latch and motorise it. Battery powered, usually with a mechanical or key override.
Where you'll find it. Growing across all door types, popular for keyless entry, holiday lets and giving trades time-limited access.
Security and insurance. Treat the underlying mechanical lock as the thing that must meet the standard (TS007 or BS3621) and the smart part as a convenience layer. Check that your specific smart lock is recognised by your home insurer before relying on it, because an unapproved smart lock can leave a gap in your cover. Ring me and I will tell you honestly whether one suits your door.
Padlocks (for sheds, gates and outbuildings) and garage door locks are a category of their own, rated by Sold Secure Bronze, Silver and Gold rather than the door-lock standards above. If you need a shed, gate or garage secured, ring me and I will spec the right grade for what you are protecting.
How to tell which lock you have
You can identify your lock in about thirty seconds without any tools. Work down this list.
- Look at the door material first. uPVC or composite (plastic, or a plastic-look slab, usually a lever handle you lift to lock) means a euro cylinder and multi-point mechanism. Solid timber means a mortice lock, a night latch, or both.
- On a uPVC or composite door, look at the key barrel poking out of the centre of the door edge or visible either side of the handle. That figure-8 barrel is the euro cylinder. The strip of metal down the door edge with hooks and bolts is the multi-point mechanism.
- On a timber door, find the keyhole. A keyhole in the face of a lock that is bolted onto the inside of the door, with a small round key, is a night latch. A keyhole in the edge of the door, worked by a chunky lever key, is a mortice lock.
- Check for a kitemark. Look on the lock faceplate (the metal strip on the door edge) or the lock body for a stamped kitemark and a standard number: BS3621 on a mortice, a TS007 star rating on a cylinder. That tells you whether it is insurance-grade.
- Still not sure? Send me a photo. A picture of the door edge and the key on WhatsApp is enough for me to tell you exactly what you have, whether it is worth upgrading, and what it should cost, before anyone quotes you a penny.
Which lock does your insurer actually need?
This is where the most expensive confusion happens, so it is worth being precise. Your home insurance policy almost certainly specifies a lock standard for your final-exit doors, and the right answer depends on the door material.
Timber doors. Most insurers ask for a five-lever mortice deadlock to BS3621, identifiable by the BSI kitemark on the faceplate. A basic night latch on its own usually does not satisfy a policy.
uPVC and composite doors. BS3621 is a timber-door standard and physically cannot be fitted to a plastic door, so insurers accept the cylinder route instead: an anti-snap euro cylinder to TS007 3-star, or a 1-star cylinder combined with 2-star security handles. If your policy wording says "BS3621" and your door is uPVC, do not panic and do not let anyone fit something that cannot exist; you need the TS007 3-star cylinder, and a quick call to your insurer will confirm it.
Getting this wrong is the difference between a claim paid and a claim refused, so if you are upgrading specifically to satisfy a policy, tell me that when you ring and I will fit, and itemise on the receipt, exactly the standard your insurer named.
What customers say about getting the right lock fitted
Verified Google reviews from homeowners across Wolverhampton, Stafford, Cannock and the surrounding villages.
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About the locksmith
The locksmith who fits all of these every week
I'm Sean Hamilton. I run Lockerfella as a one-man-band out of Brewood, Staffordshire, fitting every lock type on this page across uPVC, composite and timber doors. If you are not sure what you have or what you need, send me a photo and I will tell you straight, including when the cheapest option is the right one.
- 30+ years fascinated by locks. I've been picking, stripping and studying locks for the love of it for over 30 years. Lockerfella is what happens when a lifelong interest in how locks work becomes the day job.
- Trained and certified. Certificate of Locksmith Skills from A'Jam Locksmiths covering cylinder, mortice, padlock, wafer and euro lock picking, plus re-keying and mortice bypassing.
- Basic DBS checked, £1M insured, 12 months workmanship guarantee. Redacted DBS and insurance certificates are published on the About page, with originals available to view in person before work starts.
- One man, one van, one phone number. The phone rings on me directly. No call centre. No third-party fitter. If I quote you a price, that's the price you pay.
Common questions about door locks
Straight answers on lock types, what suits each door, and which one your insurer wants.
What are the different types of door locks?
On a typical UK home you will meet a handful of lock types, and which one you have depends almost entirely on whether your door is uPVC, composite or timber. The main ones are: the euro cylinder (the flat key barrel in nearly every uPVC and composite door), the multi-point locking mechanism (the long gearbox down the edge of those doors that the cylinder drives), the five-lever mortice deadlock (the heavy lock buried inside a wooden door, usually to BS3621 for insurance), the mortice sashlock (the same idea but with a latch as well so a handle works it), the night latch or rim cylinder (the "Yale-type" lock that sits on the face of a timber front door), the rim deadlock, and upgrade cylinders such as TS007 3-star anti-snap. There are also padlocks for sheds and gates and, increasingly, smart locks. Each one is explained in full further up this page.
What type of lock is on a uPVC door?
A uPVC or composite door uses two parts working together: a euro cylinder (the removable key barrel you can see from both sides of the door) and a multi-point locking mechanism (the gearbox hidden in the door edge that throws several hooks, rollers or bolts into the frame when you lift the handle and turn the key). The cylinder is the bit a burglar attacks and the bit you upgrade for security; the mechanism is the bit that fails mechanically over time. When people say "my uPVC lock has gone", it is almost always one of those two, and telling them apart is the difference between an £90 job and a £145 one. The uPVC door lock replacement guide walks through which is which, and the euro cylinder size guide shows how to measure a cylinder for replacement.
What lock do I need for my insurance?
It depends on your door material, and this is where a lot of people get caught out. For a timber front or back door, most UK home insurers ask for a five-lever mortice deadlock to BS3621 (the British Standard, marked with a BSI Kitemark and a kitemark stamp on the lock faceplate). For a uPVC or composite door, BS3621 usually cannot be fitted at all, and the equivalent your insurer wants is an anti-snap euro cylinder to TS007 3-star (or a 1-star cylinder combined with 2-star handles). Fitting a BS3621 mortice into a uPVC door is impossible, so if your policy says BS3621 and your door is plastic, you need the cylinder route instead. The British Standard locks guide and the anti-snap locks guide cover exactly what each door needs.
What is the difference between a euro cylinder and a mortice lock?
They are two completely different locking systems for two different door materials. A euro cylinder is a removable key barrel, shaped like a fat figure-8 in cross-section, used in uPVC and composite doors where it drives a multi-point mechanism. You can pull one out and swap it in a few minutes once you know the size, which is why a cylinder change is one of the cheapest lock jobs. A mortice lock is a heavier lock body that sits inside a pocket (a "mortice") cut into the edge of a solid timber door, with the bolt thrown by a traditional lever key. Mortice deadlocks to BS3621 are the classic insurer requirement on wooden doors. In short: plastic and composite doors take cylinders, wooden doors take mortice locks, and the two are not interchangeable.
What is a multi-point locking system?
A multi-point locking system, or multi-point mechanism, is the long metal strip that runs down the opening edge of almost every uPVC and composite door. When you lift the handle it engages several locking points at once, hooks, rollers or deadbolts, top and bottom as well as at the centre, and turning the key then deadlocks them. It is far more secure than a single central bolt because it pulls the whole door tight into the frame. The gearbox is the heart of it, and gearbox failure (the handle going floppy, or lifting but not locking) is one of the most common uPVC door faults I am called to. A like-for-like gearbox swap is from £145, far cheaper than the "whole new door" some firms try to sell. The door won't lock guide covers the symptoms.
Are smart locks any good, and should I fit one?
Smart locks (keypad, app or fingerprint operated) can be genuinely useful for keyless entry, time-limited access for trades or guests, and seeing who came and went. The honest caveats: not every smart lock suits a UK uPVC multi-point door, many retrofit onto an existing euro cylinder or night latch rather than replacing the whole mechanism, battery life and a reliable mechanical or key override matter a lot, and you should check whether your home insurer recognises the lock to the standard your policy requires. A smart lock that is not insurer-approved can leave you with a security upgrade that does not actually satisfy your policy. My advice is to treat the underlying mechanical lock as the thing that has to meet the standard (TS007 or BS3621), and the smart part as a convenience layer on top. If you are considering one, ring me and I will tell you honestly whether it will work on your door before you spend.
How do I know what type of lock I have?
Start with the door. If it is uPVC or composite (plastic or a plastic-look slab, usually with a lever handle you lift to lock), you almost certainly have a euro cylinder driving a multi-point mechanism. If it is solid timber, look at where the keyhole is: a lock buried inside the edge of the door, worked by a chunky lever key, is a mortice lock, while a lock bolted to the inside face of the door with a small round key is a night latch or rim cylinder. Check the faceplate on the door edge or the lock body for a kitemark and a standard number (BS3621, TS007) stamped into the metal. If you are still unsure, send me a photo of the door edge and the key on WhatsApp and I will tell you exactly what you have, what it is worth fitting, and what it should cost, before anyone quotes you.
Not sure what you've got?
Send a photo and I'll tell you exactly what you have
A picture of your door edge and key on WhatsApp is enough for me to identify your lock, tell you whether it is insurance-grade, and quote any change or upgrade before I set off. No call-out fee, no VAT on top, no upsell.
Page last reviewed: . Reviewed by Sean Hamilton, the locksmith behind Lockerfella, under our editorial standards.