NANIWA Flattening Stone (Truing Stone)
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.
To speed up the process still further, one can sprinkle a little Silicon carbide powder onto the block (see drawing). But if one uses the powder, the sharpening stone must be thoroughly washed with water afterwards.
The flattening block comes with removable rubber feet to prevent it from sliding around in use: