Locksmiths use a lot of shorthand, and it is no help to you when your door will not lock. This is our plain English glossary of the terms you are most likely to hear from us or read on your insurance documents. No jargon for the sake of it, just what each thing actually is.
This glossary comes from years of working doors across Hythe, Holbury, Fawley and the wider Waterside, so the words you read here are the ones we actually use on the job.
The short version:
- Plain English glossary of locksmith and door-security terms
- Covers door parts, lock types, security standards and attacks
- Euro cylinder is the most-upgraded part on uPVC doors
- BS3621 is the standard most insurers want on exit doors
- Anti-snap cylinders defend against the common snapping attack
- Non-destructive entry is our first approach on a lockout
Door and lock parts
Euro cylinder. The barrel-shaped lock you find in most uPVC and composite doors, where the key goes in. It is the part most often upgraded for security. See our anti-snap cylinder page.
Multipoint lock. The mechanism in a uPVC door that throws several locking points, hooks and bolts, up and down the frame when you lift the handle. Most uPVC faults are here, not in the cylinder.
Gearbox. The heart of a multipoint lock, the part the handle drives. When a uPVC handle goes stiff, floppy or will not lift, it is usually the gearbox. We cover this on our uPVC door repair page.
Keep. The metal plate or slot on the frame that the bolts and hooks engage into. A misaligned keep is a common reason a door is hard to lock.
Cam. The small tail inside a cylinder that turns and actually drives the lock. A worn cam is why a key can spin with nothing happening.
Lock types
Mortice lock. A lock set into the body of a wooden door, common on front and back doors. A British Standard mortice deadlock is what many insurers want.
Nightlatch. The Yale-style latch that locks automatically when the door closes. Handy, but on its own often not enough for insurance unless it is a British Standard version.
Deadbolt. A bolt that can only be moved by turning the key or thumbturn, with no spring, so it cannot be slipped or forced back like a latch.
Security standards
BS3621. The British Standard most insurers require on exit doors. Covered in full on our lock standards explained page.
Anti-snap. A euro cylinder built to break in a controlled way under attack, so a snapped section does not give access. The key upgrade for uPVC doors.
Sold Secure. A real-world attack rating run by the Master Locksmiths Association, graded Bronze to Diamond. The benchmark for key safes and high-security locks.
Kitemark. The BSI symbol proving a product independently meets the standard it claims.
Common attacks
Snapping. A common attack where a burglar breaks a weak euro cylinder to defeat the lock. Anti-snap cylinders are the answer.
Bumping. A technique using a specially cut key to pop the pins in a vulnerable lock. Better cylinders resist it.
Drilling. Attacking the cylinder with a drill to destroy the pins. Anti-drill plates and hardened cylinders defend against it.
What we do
Non-destructive entry. Opening a lock without damaging it, by picking, slipping or manipulation. Our first approach on a lockout. See non-destructive entry.
Rekey. Changing the internal pins of a lock so old keys no longer work, often cheaper than a whole new lock after lost keys.
Key safe. A small wall-mounted box holding a key behind a code, useful for carers and holiday lets when it is a Sold Secure rated one.
If you have heard a term that is not here, just ask us, or browse the Home Security Knowledge Centre for the bigger picture.
Frequently asked questions
What is a euro cylinder?
It is the barrel-shaped lock in most uPVC and composite doors that the key goes into. It is the part most commonly upgraded for security, usually to an anti-snap version.
What is the difference between the cylinder and the multipoint lock?
The cylinder is where the key turns. The multipoint is the mechanism that throws several bolts and hooks into the frame when you lift the handle. Most uPVC faults are in the multipoint, often the gearbox.
What does anti-snap mean?
An anti-snap euro cylinder is built to break in a controlled way under attack so the snapped section does not give entry. It is the main security upgrade for uPVC doors.
What is lock bumping?
Bumping uses a specially cut key tapped into a vulnerable lock to jump the pins and open it. Better quality, rated cylinders are designed to resist it.
What is rekeying?
Rekeying changes the internal pins of a lock so old keys no longer work, without replacing the whole lock. It is often the cheaper fix after keys are lost.
What is non-destructive entry?
Opening a lock without damaging it, using picking, slipping or manipulation rather than drilling. It is our first approach on a lockout because it saves you the cost of a new lock.
Need a locksmith now? Bugsy answers the phone himself, no call centre. No call-out fee. Call 07453 327708 for a quick honest quote.
Bugsy Edwards
Founder, Keywise 24hr Locksmiths. Family-run on the SO45 Waterside.
This advice comes from a working locksmith, not a content writer. Bugsy answers his own phone, and was named the Hampshire Police and Crime Commissioner's 2024 Community Volunteer of the Year. 5.0 from 288 Google reviews.
Call 07453 327708