For saw sharpening. To choose the right file, size it to the tooth. Ideally, about half of the cutting surface of the file will be in contact with the tooth -- half of the file will be in the gullet and the other half unused. When you rotate the file to get a fresh edge, it will be uniformly sharp. If you use a smaller file, only some of the new surface will be fresh and the rest dull. Made by Grobet in Switzerland. Always use a handle on a file.