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Nightlatch vs mortice lock: which bolt is the security one

Updated: October 2026

A nightlatch versus a mortice turns on where the bolt sits and whether a British Standard names it. On a timber final exit, police and insurer guidance treat a BS 3621 mortice as the stronger lock and a standard nightlatch as the one you use as well. The [door lock comparison](/hub/door-and-window-security/door-lock) has nightlatches and no mortice. The Yale 77 is the top pick for a 60 mm swap and the lowest price, so there is no separate best-value badge. That is not a BS 3621 mark. Peter F. read the listings and UK sources in October 2026, with no lab test. A qualifying purchase can earn a commission at no extra cost to you.

A nightlatch versus a mortice turns on where the bolt sits and whether a British Standard names it.

Our top picks

Yale Yale 77 nightlatch

Best overall

Yale Yale 77 nightlatch
9.2/10about £11.64
View offer
QWORK QWORK antique night latch

Rank 2

QWORK QWORK antique night latch
8.2/10about £11.99
View offer
On this page
  1. 1.What a nightlatch is doing
  2. 2.What a mortice adds
  3. 3.When you want both
  4. 4.When a nightlatch can be the rated lock

What a nightlatch is doing

A nightlatch, often called a rim lock, sits on the inside face. A spring bolt shoots into the staple as the door closes. A snib can hold that bolt back or deadlock it from inside. It is still a spring bolt on the face, not a mortice bolt in the edge. The Yale 77, at about £11.64, is that pattern: standard security, a rim cylinder and a snib, with no claim of auto-deadlocking or BS 3621. People buy it because a 60 mm hole is already there. Checkatrade describes an undeadlocked spring bolt as something that can be pushed back, including with a card. If this latch is the only ironmongery, the bolt in the edge is still missing.

What a mortice adds

A mortice is cut into the edge, so the bolt travels inside the timber. ProtectUK says embedded mortice or sash locks offer more security than rim locks, and points to five levers and BS 3621:2007+A2:2011. Allianz says a nightlatch on its own is less secure, and that many insurers then want a five-lever BS 3621 mortice as well. A deadlock is a bolt you throw. A sashlock adds a spring latch in the same case. Five levers are not the standard by themselves. The schedule is asking for the Kitemark. None of the products here is that mortice.
Yale Yale 77 nightlatch

Testsieger

Yale Yale 77 nightlatch
9.2/10about £11.64
View offer

When you want both

On a timber final exit, keep a BS 3621 five-lever mortice as the security lock and use a standard nightlatch only beside it. The nightlatch is what you close behind you. The mortice is what you throw when the house is empty, and at night if the schedule says the locks are in use. If you already have that mortice, the Yale 77 can be the second lock at about £11.64 when the holes match. Another nightlatch does not create a mortice. If you never throw the mortice, the bolt is idle. That point, including an ombudsman decision, is on the door lock insurance page.

When a nightlatch can be the rated lock

A nightlatch is the rated lock only when it auto-deadlocks and carries the Kitemark. A snib does not make that swap. Yale's BS1, from £76.99, is presented as BS 3621:2007 with a Kitemark, and it is not an ASIN here. The Yale 77 is standard security. The QWORK is not that rated nightlatch either. A uPVC multipoint is a different door. A motor on its cylinder is neither a mortice nor a BS 3621 nightlatch, and this page does not rank it. This shortlist contains neither.

Common questions

Is a nightlatch enough on its own?
On a timber final exit, a standard nightlatch is not the lock Allianz and ProtectUK describe as enough by itself. Allianz says a rim lock alone is less secure, and that many insurers want a five-lever BS 3621 mortice as well. ProtectUK says an embedded mortice offers more security than a rim lock. A nightlatch can still latch a door that is not your final exit.
What is the difference between a deadlock and a sashlock?
A deadlock is a bolt you throw, with no spring latch in the same case. A sashlock combines a spring latch and a deadbolt, so the door can catch as it closes and still take a key-thrown bolt. The deadbolt stays out until you unlock it. A nightlatch’s spring bolt is closer to the latch half of a sashlock than to a deadlock, even when a snib holds it.
Does the snib make a nightlatch a deadlock?
It holds the spring bolt from inside, so the bolt is harder to push back while you are in. ERA Protect treats that as a limit on a simple reach-through. It does not turn a standard nightlatch into BS 3621, and it does not equal an auto-deadlocking Kitemarked nightlatch such as the Yale BS1. The Yale 77’s snib sits on a listing that says standard security. You still throw a separate mortice when that mortice is the security lock.
Is every five-lever lock BS 3621?
No. Five levers describe the mechanism. BS 3621 is the Kitemarked standard ProtectUK cites, including BS 3621:2007+A2:2011 in its locks note. A lock can have five levers and carry no Kitemark. A schedule that names BS 3621 is asking for the standard on the faceplate, not for a lever count in a listing. Levers without the mark leave you short of that clause.
Should I add a nightlatch if I already have a mortice?
Yes, as the convenient second lock, when the mortice is already a BS 3621 deadlock or sashlock and the holes suit a rim latch. Neighbourhood Watch pairs a British Standard nightlatch with a British Standard deadlock. The Yale 77 can be that second lock at about £11.64 if you accept standard security and do not need the nightlatch itself to carry the Kitemark. Removing the mortice and keeping only the nightlatch would drop the security lock.
Does this apply to a uPVC door?
No. A uPVC door usually has a multipoint lock and a euro cylinder, not a rim nightlatch beside a separate mortice. The choice there is the strip and the cylinder. A motor on that cylinder is a different product, and this page does not rank it. This page is the timber question only.

Related pages

Door lock buying guide

How to fit a nightlatch

Door lock

Best door lock UK: who each shortlisted lock is for

BS 3621 door lock insurance: what the schedule asks

Sources

Public UK and manufacturer sources from the research digest, used for this page in October 2026. Prices, stars and review counts are the amazon.co.uk figures in this comparison. None of the four locks is treated as BS 3621, TS007 or Sold Secure.

  1. AA Insurance: door locks (retrieved October 2026)
  2. AXA LC01 locks requirement (retrieved October 2026)
  3. police.uk: door and window lock advice (retrieved October 2026)
  4. ProtectUK: security at home (retrieved October 2026)
  5. West Yorkshire Police: burglary advice (retrieved October 2026)
  6. Allianz: house locks (retrieved October 2026)
  7. Financial Ombudsman DRN-5526434 (retrieved October 2026)
  8. Yale BS1 nightlatch (retrieved October 2026)
  9. Master Locksmiths Association (retrieved October 2026)
  10. Nightlatch measuring guide (retrieved October 2026)