a file is a tool used to shape materials, by wearing away some of it. today, files are usually made of a steel bar that has a rough surface. by rubbing the surface against a material, some of the material is scraped away. there are also nail files used to shape a person's fingernails. files can also make a surface smooth so that there are no gaps, which is useful when two surfaces need to be attached to each other. a file is "blunt" if it is the same size on both ends, and "tapered" if one end is smaller than the other.