Finally cut a slot with a triangular file and a hacksaw. When I put the dovetail blank in, I wrote down the direction (yes, it's tapered) so I can get that out without drama if necessary. A note on the Marble aperture sight. It comes with 3 screw in apertures, and with the finest one on the bench, I was able to shoot <2" groups (100 yd). Adjusting is a little funky, as moving horizontally would also move the group vertically and vice versa. Great once dialed in, though. The fine peep looks a little tight for hunting, so I installed the middle size. Very fast target acquisition.