A key switch (sometimes called a lock switch to distinguish it from a keyswitch) is a switch that can be activated only by the use of a key. They are usually used in situations where access needs to be restricted to the switch's functions.
Key switches are available as components with solder connections, and are available with a variety of ampere ratings. They may use tubular or other specially-shaped keys for extra security.
Key switches have been used for a variety of purposes, up to and including the launch of nuclear missiles.