In metalworking technology, to gradually reduce the diameter of a metal rod or plastic cylinder by pulling it through perforations of successively diminishing size in a series of plates. Wire and various specialty filaments are made in this way; they may be either cold-drawn (without preheating) or hot-drawn (heated to softening point). Dies made of low-grade diamonds are often used for precision work. An analogous method is used in sheet-metal forming.