Use a medium sized screwdriver and lightly tap the edge of the flint with the shaft of the screwdriver while the flint is held in the lock. They won't last for as many shots as a new flint will, tho. At least mine won't. Diamond honing stones will sharpen them too. The cut agate flints respond pretty well to a diamond hone. Don't waste your time with the cut arkansas stone flints, I've never gotten one to work well.