This article deals with how to sharpen a knife correctly. And so. The knife must be sharp. And period. For what reason? For several reasons. First, the old-old rule says that you can cut yourself much harder and more painfully with a blunt knife. This is understandable, because you have to make much more effort with a blunt knife. Secondly, only with a very sharp knife can you cut the thinnest slices of the product.