Locks explained
Night Latches: Yale-Type Rim Locks and BS 3621
A night latch is the box lock on the inside face of a timber front door, often called a Yale-type lock after the old brand name. It latches as the door shuts. A basic latch adds little security on its own; a deadlocking version to BS 3621 can be locked with a key. Fitting is charged by time, at £65 to £85 an hour (MLA price list, Checkatrade and Bark).
What is a night latch?
A night latch, or rim lock, is surface mounted. A small cylinder passes through the door from outside, and a case on the inside face holds a sprung bolt that drops into a staple on the frame as the door closes. From inside you turn a knob; from outside you need the key. Most have a snib, a small slider that holds the latch back or locks the knob. The name "Yale lock" stuck because that brand made so many of them, but many makers produce them now, and on this page the term means the type, not the maker.
Where are night latches used?
You find night latches on the front doors of older timber houses, on flats with a timber entrance door, and on some back doors. They are usually paired with a mortice deadlock lower down: the latch keeps the door shut during the day, and the deadlock secures it when the house is empty. Night latches also turn up on outbuildings and on room doors in shared houses. They are rare on uPVC and composite doors, which are built around a multipoint lock instead, and on those doors the security grade sits on the euro cylinder.
Which night latch meets BS 3621?
A standard night latch only holds the door shut. It does not deadlock, and its inside knob opens for anyone who can reach it, so on its own it is not a security lock. A BS 3621 night latch deals with both points. It deadlocks, meaning the bolt cannot be pushed back once the door is shut and locked, and the inside knob can be key-locked. Look for the Kitemark and "BS 3621" on the case. BS 8621 versions keep the inside knob usable at all times, so people can get out without a key, which suits flats. An insurer may accept a BS 3621 night latch as a main lock; check the wording of your own policy.
How can you tell what night latch you have?
Look at the inside case. A Kitemark and "BS 3621" stamped on it, or on its edge, mean the latch meets the standard. A keyhole in the inside knob suggests a lockable latch, though it does not prove the standard. Note the backset, the distance from the door edge to the centre of the cylinder: 60 mm is the common size and 40 mm the narrow one, and a replacement needs to match the holes already in the door. The cylinder is usually a separate round rim cylinder, which can be changed on its own if keys are lost.
What does a night latch cost fitted, and when should you call a locksmith?
There is no separate sourced price for a night latch, so the honest guide is time. Locksmiths charge £65 to £85 an hour in the daytime (MLA price list, Checkatrade and Bark), and the MLA lists London from £95 an hour. A like-for-like swap into existing holes is a short job; moving to a different backset means filling and recutting. Spare keys for a standard rim cylinder cost £4 to £7 each (MLA key cutting prices; Home Secure Shop). If you are locked out, most night latch lockouts are opened without drilling, and the MLA, MyJobQuote and Fantastic Services put a daytime lockout at £90 to £160.
Common questions
Is a night latch enough security on a front door?
A basic night latch alone usually is not. Insurers commonly expect a BS 3621 mortice deadlock as well, or a BS 3621 deadlocking night latch. Check the exact words in your own policy.
Why is it called a Yale lock?
Yale made the pin cylinder and rim latch familiar in British homes, so the name stuck to the type. Plenty of makers produce night latches today, and the standard on the case matters more than the name.
Can a night latch be fitted to a uPVC door?
It is uncommon. uPVC and composite doors are built around a multipoint lock with a euro cylinder, and their security grade sits on that cylinder rather than on any latch added to the face.