The fixer swivel rotates at 90 degrees around an axis and the fixer is tightened by tightener (20) having rule joint with cross bar and a clamping screw (22) on the support. The device further comprises: a stopper having guidance and rod, which limits the movement of the pivot； a locker having a bolt, which swivels around the axis is parallel to the axis of the top table； and a blocker having an index. The movement the pivot is guided by guider having rib (27) and a slot (6). A hall effect sensor (45) with magnet (13) detects the positioning of the object.
