Deadlocking nightlatch with 40mm Backset - Recommended for doors where there is a restricted width to mount a lock. Inside handle can be deadlocked by a reverse turn of the key in the outside cylinder after closing the door. Key operation from outside and lever handle on the inside. Snib function enables the latch to be held back. Latch can be deadlocked by the snib button internally, making the lock inoperable by key or handle.