Files are made of steel sections, cut and shaped precisely to meet requirements for the working material. After preheating and softening the steel, teeth are struck out by a chisel. Files differ by type of steel, the form of the grinding part, the depth and smoothness/roughness of the cuts (teeth). A file is a valuable addition to any tool set, and even it's not used as often as it was before industrialization, files still find regular application in metalworking, woodworking, and similar industries.