"Flat is the foundation of any sharpening system….flat backs, flat bevels, flat tools and flat sharpening stones. Why is flat important? The sharpest cutting edge is the intersection of two perfectly flat areas of the tool, the bevel and the back. Since the surface of the tool will mirror the stone it was sharpened on, is critical that the sharpening stone be flat. The Diamond Glass Lapping Plate, is flat to ± 5 microns, and will easily return Shapton stones to perfect flatness. Keeping your stones flat means sharpener tools, but it will also ensure even wear for a longer stone life. For optimum sharpening results, Shapton stones must be flattened after each use.