and screw retaining screw 22 is then installed in the threaded bore 26 in the head of the cap screw and tightened to bring cleats 39 into binding engagement with the top surface of the cap screw and or lock plate depending upon the relative thicknesses of the two once installed the locking fasteners prevent the screws that secure the cover to the box from working loose and the tamper proof retaining screws prevent the cover screws from being removed without a special tool or key that matches the drive sockets in the heads of the retaining screws the embodiment illustrated in fig3 and 4 is generally similar to the embodiment of fig1 and 2 and like reference numerals designate corresponding elements in the two embodiments here again the fastener includes a cap screw or bolt 19 a lock plate 21 that prevents the cap screw from working loose and a tamper proof retaining screw 22 that keeps the lock plate on the cap screw and the fastener secured in place in this embodiment however the cap screw has a 12 point flanged head 44 rather than a 6 point hexagonal head in addition to the cap screw lock plate and retaining screw the embodiment of fig3 and 4 also includes an insert or adapter 46 for use in counterbores which.