Knife Sharpening Stone, WAYCOM Whetstone for Wood Carving Kit (Millstone) Cylindrical Whetstone: Used for the Curved knife, Inner arc knife and other Round knives. Rectangle Millstone: For Flat knife, Beveled knife and other Flat knives. Triangle Sharpening Stone: Perfect for Triangular knife and other Inside tip shaped knives. Perfectly sharpen any type of Craving knife quickly and easily.