Left Handed Entrance and Apartment Mortise Lock Entrance and apartment mortise lock with 2-1/2" backset Handleset x Knob / Lever Latch bolt by thumb piece outside and knob inside, except when thumb piece is locked by stop in front; then latch bolt by key outside and knob inside. Deadbolt by key outside and turn piece inside. Continuous turn of key outside retracts both latch and deadbolt. 1" (25mm) throw deadbolt with saw-proof inserts is standard equipment. When extended, deadbolt deadlocks latch bolt. For single and double cylinder applications