PURPOSE: To increase the strength of lock-body front ends by inserting the U-shaped lock-body front ends into lock holes formed at both ends of a pipy lock and engaging and disengaging pin-shaped members into lock holes formed to the front ends and conducting locking and unlocking.

CONSTITUTION: Both end sections of a lock body 40 are inserted into an inserting hole 52 and the housing section 88 of a restraining hole 84 through key holes 32, 33. When a key 102 is rotated and a displacement member 90 is turned in the counterclockwise direction up to a specified place in the case of locking, two projecting surface sections 92 are positioned on the left-right opposite sides and attached closely to two projecting lugs 86. An interlocking member 80 and an interlocking lever 60 compress a spring 70 and are moved to the left while a projecting pole 87 and the left end section of the lever 60 are penetrated into through-holes 42 and the lock body 40 is clamped. When the key 102 is revolved in the clockwise direction in the case of unlocking and the member 90 is rotated up to a specified place, the lug 86 does not receive the pushing of the projecting surfaces 92. The lever 60 and the member 80 are moved to the right by the spring 70, and the projecting pole 87 and the left end of the lever 60 are slipped off from the holes 42. Accordingly, since no open groove is formed at lock-body end sections and engagement and disengagement are conducted by the holes, strength can be increased.