To provide a key which does not disturb a pass or a use by making the length of the key protruding from a key hole to the outside as short as possible and can be used in the same way with an ordinary key when locking, in a key retained in a lock in an unlocked condition.

The key is retained in a lock in an unlocked condition. A knob 7 of the key formed separately from the external end 5 of a key body 4 is rockably connected by a hinge shaft 6 so that the knob 7 can be perpendicularly folded to the key body 4.