This professional double-sided knife sharpener grindstone is a tool that can be used to sharpen, repair, and polish cooking knives. It has two sides, one with a coarse grit and one with a fine grit, which allows you to sharpen your knives to different levels of sharpness. The coarse grit is used to remove any major damage to the knife's blade, while the fine grit is used to polish the blade and give it a sharp edge.