an angle with respect to the lag screw centerline 32 shown as anti rotation flats angle 209 in this embodiment this angle is 0 5 degrees the result of the anti rotation flats angle 209 is that the anti rotation flats distal breadth 202 is greater than the anti rotation flats proximal breadth 204 it is the interaction of the sloped anti rotation surfaces 208 with the lock screw button 102 that controls the amount of relative longitudinal motion permitted between the nail assembly and lag screw assembly the lock screw thread locking element 124 is made of a material that is softer than the material used in the nail proximal internal threads 84 into which the lock screw thread locking element 124 threads such softer materials include certain metals such as copper or non metal materials such as plastic the lock screw thread locking element 124 is also sized to be slightly too large for the nail proximal bore 80 this creates an interference fit between the lock screw thread locking element 124 and the nail proximal internal threads 84 the interference fit in turn creates resistance preventing the lock screw from rotating freely and loosening the connection between lock screw button 102 and the lag screw 200 the lock screw thread locking element 124 includes a gap 125 to aid in assembly it is anticipated that the lock screw thread locking element be made from two or more separate pieces or without a gap 125 at all if the lock screw thread locking element 124 is sufficiently flexible to be stretched over the lock screw body 100 all the internal parts of the nail assembly are cannulated or with.