What Is a 5 Lever Mortice Lock? Explained Without the Jargon

A five-lever mortice lock is a deadlock fitted into the body of a door — the mechanism is concealed, the bolt throws into the frame, and there are five levers inside that have to align precisely for the key to turn. That last part is what matters for security.

Quick answer

• Five levers = more key combinations = harder to pick
• "Mortice" means the lock body is set into the door itself, not screwed to the surface
• British Standard (BS 3621) is the insurance-grade version — most home insurers require this
• Timber external doors should have one; uPVC and composite doors use multipoint locking instead
• Full price breakdown for fitting one

What "five lever" actually means

Inside every mortice lock is a set of levers — metal plates that have to lift to the correct height before the bolt can move. A two-lever lock has two of them, a five-lever has five. More levers means more possible key profiles, which makes it harder to pick or to cut a copy key that accidentally works.

Two-lever locks are fine for internal cupboards. Three-lever is common on older front doors and some shed locks. Five-lever, especially to British Standard, is what your insurer is likely asking for on external doors. A basic five-lever isn't the same as a British Standard five-lever — the BS version adds hardened steel anti-saw plates, anti-drill pins, and a bolt that resists attack. Always check the lock has the BS 3621 kitemark before assuming you're covered.

(John's note: most of the time when someone says "I've got a five-lever", they actually have a three-lever. Easy to check — it's usually stamped on the faceplate.)

Mortice vs rim lock — what's the difference

A rim lock is surface-mounted on the inside face of the door. A night-latch (the kind where you slam the door and it clicks) is almost always a rim lock. These are fine for an inner latch but provide minimal security on their own.

A mortice lock is set into a slot cut in the door edge. It's the bulkier of the two, usually requiring a key from both sides, and it's what insurance policies are referring to when they say "approved deadlock".

A good external timber door typically has both: a rim night-latch so you can pull the door shut behind you without a key, plus a five-lever mortice deadlock that you use when you're leaving for any real length of time. If you've only got one of them, you've got half the job done. See the lock change page for what that looks like in practice.

How to check what you've got

1. Look at the edge of your front door. If you see a rectangular metal plate with a bolt hole, that's a mortice lock.
2. Look at the face of the lock body or that plate for any markings — "BS 3621", "5 lever", or a kitemark symbol.
3. Check the keyhole. A traditional mortice lock keyhole is the classic vertical slot with a round top (like a cartoon keyhole). That's distinct from the oval of a euro cylinder.

If you can't find any markings and you're not sure, take a photo of the key and call us. The key profile usually makes it obvious.

When NOT to worry about a five-lever mortice

For uPVC and composite doors — the ones with a long strip of visible locks down the edge when you open the door — you don't need a mortice. These doors use a multipoint locking system, typically with a euro cylinder. Your insurer will have different requirements for these, usually asking for an anti-snap cylinder rather than a five-lever mortice.

For internal doors — a two or three-lever mortice is fine. No insurer is asking you to put a British Standard deadlock on your bedroom door.

Prices for fitting one in Barnet

| Job | Price | |---|---| | Labour only (door already prepped) | £61 per lock | | Basic 5-lever mortice supplied and fitted | From £160 all-in | | British Standard BS 3621 anti-drill version | £219–£699 all-in | | High-security British Standard with insurance card | £350–£699 |

See all locksmith prices for the full list.

Sign-off

If you're in Barnet or North London and genuinely unsure whether your front door meets your insurer's spec, call 020 3780 8827 before you need to find out the hard way — i.e. after a claim. John will check on site and tell you what's there, what it needs, and what it'll cost before touching anything.