To finish the end face outside a bush with good appearance and to facilitate insertion of a key tip.

A door 3 mounted in an entrance of the unit room A to be freely openable and closable is provided with a locking means 16 for locking with the door 3 closed. An internal operation lever 16 for locking and unlocking the locking means 16 is provided on the surface of the inside of the unit room A of the door 3. A bush 17 capable of inserting a key 18 for working from the outside of the unit room A into the interior is rotatably mounted on the surface of the outside of the unit room A of the door 3. A cap 22 is intergrally provided on the end of a key tip 21 having the same sectional form as that of the key 17 for working to form a cap 12 with the key tip, and a coin groove 20 is formed in the outer surface of the cap 20. The key tip 21 is passed through the bush 17, the tip of the key tip 21 is connected to the locking means 16, and the cap 22 is put on the outer end part of the bush 17.