What sort of lock or latch do I have?
(Locks can come with different keyhole profiles - see article on identifying lock keyhole profiles to help you choose.)
Door locks come in several basic types:
1. Dead Locks. A simple locked or unlocked mechanism operated by a lever or cylinder lock.
2. Door Latch. A sprung catch that keeps the door closed once shut. It is not a security device. The own shown here is a tubular latch but you can also get upright latches.
3. Sash Locks. A combine Dead Lock and Door Latch. Can be mortice (fits into the door) or rim (screws onto the door face) fit.
4. Bathroom Locks. The lock part of Bathroom Dead Lock and Bathroom Sash Lock is operated by a spindle, not a key, and is used with a Bathroom Turn and Release (with safety unlock feature).
6. Nightlatches (often just called "Yale" locks although this is strictly incorrect; Yale is a brand covering many different types of lock).
7. Detainer Mortice Locks for Sliding doors.