PURPOSE: To generate a stably locked state with the weight of a clamp by interlocking it with a handle receptacle while they are allowed to rotate in the opposite dirctions, and permitting the clap to generate locking in the condition that it takes a position sunk from above.

CONSTITUTION: When the tip of the shank 63 of a handle 61 is inserted in a recess hole 36 provided in a handle receptacle 31 and the handle 61 is rotated in the A direction, a clamp 10 is rotated through a notch provided therein detained with a pin 34 on the receptacle 31 in the B direction which is opposite the handle rotating direction. In the position that the clamp 10 and an arm 33 of handle receptacle 31 age sunk a certain angle from above, the clamp 10 is detained with a frame, and locking is generated. Accordingly a stably locked state is obtained with their own weights. Disengagement is made by rotating the handle 61 in the direction opposite to the direction A.