PURPOSE: To provide a fine design and improve reliability by firmly engaging a hook on the side of a body with a pin on the side of a case after a body has been pushed in to enable an operator to confirm locking.

CONSTITUTION: When a key inserted into a lock 3 is turned in a normal direction, a main lever 4 makes contact with a first contact lever 15 to rotate an intermediate rotating means 10 in a normal direction, whereby a hook 5 is rotated from a closed point to an open point, allowing the hook to be disengaged from the pin 6. When a body 2 is drawn out, a fixed contact part 20 comes into contact with a part 8 to be contacted of a part to be engaged to rotate the means 10 in a reverse direction, whereby the hook 5 returns from the open point to the closed point. When the body 2 is pushed in, since the hook 5 is rotated when a second contact lever 17 contacts the part 8 of the part to be engaged, the closed point is maintained and then the hook contacts the pin 6 and is engaged after being displaced, following which the key inserted into the lock 3 is turned in a reverse direction, whereby the lever 4 returns to the closed point and the key is pulled out to finish locking.