ABLOY LC302 mechanical lock
Function is determined by sliding snib on forend
When the snib is in its up position, the lock will deadlock when the door is closed and can only be opened by a key or by the thumbturn
When the snib is in its middle position, the lock will latch normally, but can be opened by the handles as well as the key and the thumbturn
When the snib is in its down position, the latchbolt is retained inside the lock case