A rear loaded part for attaching to a mounting plate having a mating part with a pair of parallel side walls each having a proximate end attached to the mounting plate. An upper surface, which extends between the pair of parallel side wall, includes an aperture and an elongated rib extending parallel to the pair of parallel side walls. The rear loaded part having a pair of parallel guide rails with a proximate end and an opposite distal end. The pair of parallel guide rails extends outwardly from the rear loaded part to define an elongated channel which is dimensioned to receive the elongated rib of the mating part. A pair of tabs extends outwardly from the pair of guide rails, and are dimensioned to snap into the aperture of the upper surface to releasably lock the rear loaded part to the mounting plate.