Deadlocking nightlatch with 40mm Backset - Recommended for doors where there is a restricted width to mount a lock Suitable for Timber & Glass-Panelled Doors For Doors 38-57mm Thick Inside handle can be deadlocked by a reverse turn of the key 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 High Security Suitable for Timber & Glass-Panelled Doors For Doors 38-57mm Thick Inside handle can be deadlocked by a reverse turn of the key 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 High Security