An arm assembly with an arm, a plurality of vertical support members and a horizontal member is telescopingly mounted in a housing, such that the arm assembly moves vertically by movement of a scissors mechanism having slidable pivot mountings, whereby movement of a linear actuator at the bottom of the housing translates horizontal movement to vertical movement, which vertical movement is imparted upwardly by a spring and downwardly against the spring, the vertical movement being controlled by a lever and cable actuated lock.
