An Eperon is a strange shape but typical to French stoneworking professionals. An Eperon is extremely efficient in shaping your work.
The Eperon shape is unique being a combination of two shapes.
Knife shape with a cut edge and the inusually termed "Crete de coq" which has a spur as shown in the photograph.
The Eperon is stitched on both sides. The longer the tool the more aggessive the cut.