This diamond "commode" ensures that your sharpening stone remains "open" and flat on the grinder. The sharpening stone then works more efficiently and the surface of the sharpening stone is flattened. As the sharpening stone becomes rougher, it is less likely that the chisel will "run hot". Since your sharpening is also nice and flat, you can sharpen more easily. Now you can make your chisels not only sharp, but also flat! The active surface of the commode is approx. 1.3 x 5 cm.