When the straight sided recess is to depth, the triangular file w/ the safeside down starts the dovetail and then the upsetting chisel is used to get the finished size...this is done only on bbl lugs. The raised steel is then pounded down onto the lug for a very tight fit. All the surfaces are smoothed w/ a file. The same thing is done for the rear sight dovetail except the sight is fitted using the triangular file and the raised steel is filed into a molding. The front sight is done w/o the upsetting chisel. The moldings on both sides of the rear sight enable a very shallow actual depth into the bbl {.030} but the effective dovetail depth is 1/16"......Fred