Single Cylinder Keyed Entry: Single cylinder handlesets are keyed on the exterior with an associated thumbturn on the inside that unlocks the door. The exterior handle has a thumb plate and the interior handle features a lever or knob. Single cylinder locks are most commonly used to secure entrances to a residence or place of business. Comes with Emergency Egress function which features an interconnected lock to simultaneously retract the deadbolt and door latch to quickly open your door.