If the rings installed on the rifle are not in perfect alignment a scope cannot be expected to perform properly and if the problem is severe enough, damage to the scope could result. The PTG alignment reamer is installed in the mounted rings and turned clockwise just as a chambering reamer. If the rings are not in perfect alignment metal is removed from the inside of the rings until both align with each other. One end of the cutter is turned to 1/2" diameter for use in a drill press/lathe, or may be turned by hand with a 7/8" wrench. Wrench not included.