the present invention is a mechanism for releasing a positioning device from a locked position . the positioning device has a moveable wedge urged against a rotatable cammed member which permits rotatable travel of the cammed member in only one direction . the releasing mechanism comprises a lever attached to the wedge and engageable with the cammed member . engaging the lever with the cammed member urges the wedge away from the cammed member to permit rotation of the cammed member in either direction .