The present invention is directed to a release mechanism for removing andor releasing a locking cap from the head of a bone anchor in situ. A door frame cover having an edge that is configured to conform with the shape of the door frame proximate to the floor. Apertures for hooking the receptacle on a wall are located in the rear wall in alignment with corresponding apertures in the mounting tabs at the rear for increased strength. A first plunger is sized to pass through the first chamber section and not the second chamber section.