as the guide 510 the other interior end of the driving body 500 has a larger hexagonal cross section and called the spring cavity 210 the lower retainer 130 provides a hard stop to the movement of the driving body 500 in the direction of the shank 110 portion of the mounting body 100 fig1 3 and 4 b show a cylindrical element serving as the lower retainer 130 that is roughly the same diameter as the driving body 500 fig4 a shows a different embodiment that uses a thin snap ring as the lower retainer 130 the spring 200 is mounted in the spring cavity 210 the differing interior constructions between the spring cavity 210 and the hexagonal guide 510 sections of the driving body 500 keeps the spring 200 in place because the spring 200 has round coils that are too large to escape into the smaller dimensioned guide 510 section as shown in fig3 a 3b and 4a an upper retainer 800 typically a snap ring is mounted in the spring cavity 210 as shown on fig2 4 once installed the upper retainer 800 establishes the position of the spring 200 an optional barrier plate 900 currently consisting of a non metallic material covering exterior side of the upper retainer 800 typically a snap ring provides separation between metal shavings and the device as shown in fig2 4 the barrier plate 900 is set into a grove on the inside of the spring cavity 210 creating a nut cavity 230 in which the user can place a machine screw the barrier plate 900 protects the nut cavity 230 from damage and excessive wear.