The whetstone we often use can be divided into two kinds: natural and artificial whetstone. In the market, there are three common whetstones: terrazzo, whetstone and diamond sharpening stones. Terrazzo and whetstone are natural whetstones. Diamond stones and ceramic whetstones are man-made whetstones. As we know, before sharpening the knife, the whetstone should be lubricated with water and oil.