The rattail (1) is a cone-shaped or cylindrical file or rasp. The first is to sharpen some saws with large teeth, eg a pit saw, the second is to clean small holes or arcs.
This hand tool can be distinguished from the drill saw. [MOT]
(1) Also ramasse (e.g. N.L.I.) to indicate the long cylindrical rasp that widened the cavity for the ramrod of the rifle