A French skive is a very useful and multipurpose leather craft tool.
It can be used in the same way as a edging tool to take the sharp edges off heavy leathers, and by changing the angle that you hold it at, it can also be used to skive down edges and ends.
Thirdly, if you need to thin down a small area of heavy leather to fit a popper / press stud or similar, the french skive can be used in a circular fashion to chamfer down the edges of a punched hole.
This tool is easily sharpened by rubbing the underside of the blade on a fine sharpening stone or strop. The cutting edge is 12mm wide.