As noted above, files are used for a variety of applications. This is a flat file, but other files are round, half round, triangular and many other shapes. The 10″ Nicholson file teeth are bastard (Meaning intermediate). An intermediate is used for filling that doesn’t require precision. There is also second-cut, smooth and dead smooth. This file is a mill file or single cut. A mill or single cut means the file has one set of parallel teeth. There are also cross cut or double cut. All this means is there is a second set of teeth set to an angle from the first teeth.
On some files you will see a number 1, 2, and up. All this means is 1 is more coarse than a number 2, and so on. The file we have happens to be a number 5.
As we said, a file can be designed for any use. This Nicholson file is designed for sharpening mill or circular saws , but can also be used for draw-filing and finishing metals.