Leather hand skivers are manually-operated tools for removing thin layers of leather material. They have very sharp blades that are usually either flat, or slightly curved. Skivers are drawn across leather, with downward pressure applied. They shave off a thin layer of leather as they are drawn.
Flat bladed will shave leather in an even way. Curved skiver blades will shave more towards the center of the blade, since that can cut deepest into the material. Curved blades work well for skiving out curved recesses, or for finely controlling the cutting depth but utilizing the narrower blade heights towards the edges of the curved blades.
Hand skiving is effective, though requires practice to produce a consistent result. As each pass is performed manually, the process can yield natural variations.