segment 236 each widened head segment 234 has a hexagonal shaped socket or any other suitable configuration socket 235 to accommodate a driving tool for rotating the bolt member 232 each respective shaft segment 236 extends respectively through the interior bores 220 and 221 of the lower mount 214 from the proximal side 216 to be threadably engaged with the stock bar clamp for fastening the lower mount 214 thereto when the short bolt members 232 are secured to the stock bar clamps the head segments 234 rest respectively within the countersunk cavities 226 of the lower mount 214 referring to fig1 through 17 the upper mount 215 has a first section 268 a middle section 269 a second section 270 a distal side 238 a proximal side 240 a first pair of opposite vertical interior bores 242 which is located adjacent to one end 272 of the upper mount 215 and extend through from the distal side 238 to the proximal side 240 and a second pair of opposite vertical interior bores 243 which is located adjacent to the other end 274 of the upper mount 215 and extend through from the distal side 238 to the proximal side 240 the middle section 269 has a hollow space 271 with two opposite parallel aligned bars 276 integrally connecting the first and second sections 268 and 270 of the upper mount 215 each interior bore 242 and 243 has a countersunk cavity 246 located on the.