A night latch is lock that is fitted on the surface of a door; it is operated from the exterior side of the door by a key and from the interior side of the door by a knob. Night latches are usually rim locks, and are available as dead¬-locking (automatically locks once shut) and non dead-locking versions. Historically, such locks were intended for use at night-time, hence the name. The keyless egress that they offer is a valuable fire safety measure.