Roll Sharpener: Metal Knife Sharpener (for Double-edged blades) *Compatible with stainless steel, steel, titanium knives. Fine ceramic whetstone has been patented into the shape of links so it can be easily re-sharpened. Similar to sharpening using a manual plate whetstone, it sharpenes vertically to restore its sharpness and last for a long time. How to use: 1. Put the knife into the guide groove. 2. Rough grinding and finishing sharpening can be done at one time by simply moving it back and forth about 10 times. The links can be removed and washed.