the spring element is constructed of nitinol in other aspects the spring element is made of rubber or flexible plastic in another preferred embodiment the blocking element attached to the apparatus by the spring element is allowed to slide laterally by the spring element but blocks the fasteners from backing out from where they were installed affixing the apparatus to the bone thus the sliding blocking element may be slid to the side for the installation procedure but will still have sufficient tension to prevent the bone screws from backing out from where they were installed affixing the apparatus to the bone in another preferred embodiment the blocking element operates so as to not rest on top of the fastener for example a bone screw while retaining the screws onto the plate for example the blocking element blocks only a portion of the screw from backing out from the bone but still allows access to the screw head the blocking element may only block a small portion of the screw head and still retain the screw in the bone further the blocking element may act on a part of the screw other than the screw head for example the threads of the screw in some of the illustrated embodiments the spring element is placed in a receiving portion of a plate below the location of a sliding blocking element the sliding blocking element may be used to block the removal and or rotation of bone screws a respective head of such a screw being positioned adjacent an end of the slide in particular the end of the head preferably in some embodiments overlaps an edge of the head of a particular bone screw in some embodiments a single slide blocking.