There are those (whom I respect) that still sharpen a blade only with a file leaving tiny serations in the blade. There is a specific technique to sharpening this way andserations are so tiny that they can not be seen with the naked eye. The bladesare still extremely sharp, but they are not sharpened as a scalpel would be. The reason for doing this is to keep the blade as sharp as possible after the blade penetrates the initial hair, hide, and rib cage.

Personally, I do not sharpen this way, but, there are people who do and are very successful.