The Yale 85 series deadlocking standard nightlatch security locks are some of the most widely-used front door latches. They are key operated from the outside and lever handle operated from the inside. The latch automatically deadlocks on closing the door and the snib function (bolt hold back button) enables the latch to be held back. The inside handle can also be deadlocked by a reverse turn of the key in the cylinder giving additional security (when deadlocked in this manner the latch cannot be opened from the inside only from the outside with the key) Supplied with 1109 Cylinder. Finish: Brasslux, Chrome or Dark Metal Grey (DMG). The 85 series security nightlatches have a 40mm backset, this is the measurement from the edge of the door to the centre of the keyhole. Locks with a 40mm backset are normally used where there is restricted space, such as on a narrow glass panelled door.