Night latch
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 deadlocking and non-deadlocking 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.
