Abstract: A pair of elongated arm members are provided disposed in generally the same plane and including one pair of overlapped ends pivotally interconnected for relative swinging of the arm members about an axis generally normal to the aforementioned plane. Lock structure is shiftably supported relative to the overlapped ends of the arm members and is movable between a first active position locking the arm members in adjusted angularly displaced positions relative to each other and a second inactive position allowing at least substantially free relative angular displacement of the arm members. The ends of the arm members remote from the overlapped ends thereof include non-circular recesses formed therein for receiving nuts or bolt heads therein against rotation of the nuts or bolt heads relative to the arm members and the lock structure is shiftably supported from one of the overlapped ends of the arm members for limited displacement along the axis of relative oscillation of the arm members.