Sash Locks

A sash lock combines a sprung latch and a deadbolt in one mortice case, so a single lock both holds the door closed in daily use and locks it with a key when you want it secure. It is the standard lock for a door that needs both functions, which is why it appears on most back doors and lockable internal rooms.

Measuring a sash lock

Three dimensions have to match: the case size, the backset from the door edge to the spindle centre, and the centres between spindle and keyway. Get the centres wrong and the handle will not line up with the keyhole, whatever the finish.

Where you only need a key and no handle, use a dead lock; where you only need a latch, see locks and latches. Bathrooms take a privacy version from bathroom locks. Add matching escutcheons and a handle from door handles.

Sash lock or dead lock

A sash lock combines two functions in one mortice case: a sprung latch operated by the handle for everyday use, and a deadbolt thrown by the key for security. A dead lock has the bolt only and no latch, so it is used alongside a separate latch or on a door that is never held closed by a handle. If a door needs both a working lever and a key, the sash lock is the correct choice.

Backset, centres and case size

Three measurements decide whether a sash lock will fit. The case size is the depth of the lock body into the door edge, the backset is the distance from the door edge to the centre of the spindle, and the centres are the distance between spindle and keyway. Replacing an existing lock means matching all three or re-cutting the mortice and the handle holes. On a narrow stile, a shorter case is often the only option, and on a glazed leaf check there is enough solid timber before you cut.

Fire doors and finishes

On a certified door the lock must be compatible with the door's test evidence, and an intumescent pad goes behind the case as standard, alongside fire rated hinges and the guidance in our fire door guide. Sash locks here come from Deanta, Atlantic UK Hardware and D2F Accessories with satin and polished forends to match the lever. Pair with escutcheons, browse locks and latches for the full range, and see door handles for the levers that suit.