A sharpening stone flattening block is used to dress stones that are no longer flat enough to sharpen properly. A flat stone is indispensable for effective sharpening, especially with flat blades like chisels and plane irons. To quickly flatten a stone, one simply moves it over the surface of the flattening block with a circular or back and forth movement. A steel flattening block should be used only with Silicon carbide powder. A Silicon carbide flattening block can be used without powder but you can speed up the process still further when you sprinkle a little Silicon carbide powder onto the block. The latter method is strongly recommended for hard stones i. e. the Shaptons. But if one uses the powder, the sharpening stone must be thoroughly washed with water afterwards.