according to my leather craft tools book by Al Stohlman that is a Bisonette edger "and were used by the early saddle and harness makers" and they can be used in a pushing and pulling motion like Johnv474 has stated
I have achieved this by casing, stamping, applying super sheen as a resist to the stamping using a small fine tipped paintbrush, let it dry and then apply the stain/dye
Never done that before but something that im thinking about. Quick google search took me here http://www.motherearthnews.com/diy/sewing-rabbit-fur-zmaz83jfzraw.aspx