A fingernail smoother, also known as a nail FILE, is a tool used to shape and smooth the edges of fingernails. It is usually made of metal or glass and has a rough surface that can be used to FILE down the nails. The FILE can also be used to remove dirt and debris from underneath the nails. Fingernail smoothers are available in a variety of shapes and sizes, and can be used to create different looks for the nails.