Take a .38 shell, knock the primer out, drill a 3/16 hole thru the primer pocket. Drop a 1/2" long # 10 screw thru from inside, put # 10 fender washer on then a wingnut. To sharpen wingnut take 9" sidecut pliers,and barely grab edge of wings and cut.It will shear off metal to a razor edge. You can also cut slots into the washer and bend triangle pieces forward to make it even deadlier. You can also put the wire between the shell and the washer for even more grab. Points made like this cost pennys to build.