Early European saws were made from a heated sheet of iron or steel, produced by flattening by several men simultaneously hammering on an anvil (Barley ibid p11) After cooling, the teeth were punched out one at a time with a die, the size varying with the size of the saw. The teeth were sharpened with a triangular file of appropriate size, and set with a hammer or a wrest (Moxon, ibid). By the mid 18th century rolling the metal was usual, the power for the rolls being supplied first by water, and increasingly by the early 19th century by steam engines. The industry gradually mechanized all the processes, including the important grinding the saw plate "thin to the back" by a fraction of an inch, which helped the saw to pass through the kerf without binding (Moxon, ibid, p95). The use of steel added the need to harden and temper the saw plate, to grind it flat, to smith it by hand hammering and ensure the springiness and resistance to bending deformity, and finally to polish it (Barley ibid pp5–22). Most hand saws are today entirely made without human intervention, with the steel plate supplied ready rolled to thickness and tensioned before being cut to shape by laser. The teeth are shaped and sharpened by grinding and are flame hardened to obviate (and actually prevent) sharpening once they have become blunt. A large measure of hand finishing remains to this day for quality saws by the very few specialist makers reproducing the 19th century designs.