The image to the left shows a selection of needle files in an assortment of cross sectional shapes.
Needle files are small files that are used in applications where the surface finish takes priority over metal removal rates but they are most suited for smaller work pieces. They are often sold in sets, including different shapes.
Files have forward-facing cutting teeth, and cut most effectively when pushed over the workpiece. Pulling a file directly backwards on a workpiece will cause the teeth to bend, permanently damaging the file (especially when an inexperienced user adopts a back-and-forth "sawing" motion).