What's this key slot for?

Bathroom Door Lock royalty-free images door slot lock Buy Stainless Steel Door Mail Slot with Extra Large Mail Catcher and Combination Lock door mail slot catcher lock shown below What is a mortice style lock? Mortice is a carpentry term meaning a slot or recess cut out of a piece of wood, so that another piece with

door letter slot Cam 1 34 long Includes Jackpot Reset Key #2341 This lock allows for the key to be removed when the door is locked or when open