Japanese Vätsten 240 Grit from Satake, also called whetstone, is excellent for repairing damage in the edge of the knife. It gives a basic sharpening, but to make the edge really sharp, you need a finer sharpener. Whetstones are graded according to grit, or degree of fineness, depending on the purpose of the grinding. Satake sharpening stones are color coded to clearly show their grit, and the packaging matches the color of the stone for easy identification.