Abstract: A limiting stop for the swinging angle of an arm which is pivotally mounted on a fixed structure. The stop consists of a pair of parallel links which are connected for relative sliding motion between at contracted position and an extended position. At least one of the links has an elongated slot and the other link has a laterally projecting tongue which extends into the slot for movement along the slot. One end of the slot has a stopping surface which is engaged by the tongue when the links are in the extended position for determining the swinging angle of the arm.