For racking a movable switchgear unit into and out of its enclosure, a racking mechanism is disclosed which comprises a jackscrew mounted on the movable switchgear unit, a traveling nut mounted on the jackscrew, and an anchoring device mounted on the enclosure having an opening receiving a lug on the traveling nut. A housing for the jackscrew contains a first slot extending axially of the jackscrew for holding the lug in said opening in the anchoring device during racking movement. The jackscrew housing also contains a second slot perpendicular to the first slot into which said lug can be moved when the nut is being uncoupled from the anchoring device. Friction means causes the nut to rotate with the jackscrew when the nut is properly positioned for uncoupling from the anchoring device, thereby causing jackscrew-rotation under these conditions to move the lug from the opening in the anchoring device into said second slot.