I just recently purchased a Hepburn .22 that had an open dovetail where the front sight was removed. I decided to make a filler for it out of a piece of ebony I had in my toolbox for years. I cut a small piece and hand filed a dovetail that tightly fit the barrel slot. I masked the barrel for protection and hand filed and sanded to the barrel contour. I left it just the tape thickness proud to avoid getting into the surface of the barrel. I cleaned the dust and simply oiled the surface to complete the job. Turned out pretty well.