To dispense with a bucket link when a clamshell is mounted on a hydraulic shovel and used as an operating tool and prevent damage to an arm due to the oscillation of the bucket link and noise due to the contact of the arm when the bucket link remains mounted.

Brackets 11, 12 are fixed to a bucket link 6 and an idler link 5, respectively, and fastened with bolts, a protrusion is firmly provided for the bucket link 6 and a protrusion receiver is firmly provided for an arm, both being engaged each other, or a stopper is firmly provided for the idler link 5 to restrict the oscillation of the bucket link 6.