It is the forging. The selected Watetsu / Wakoh is tempered in 1100 - 1300ºC to get the toughness and the resistance on the rust. The process of the temper is repeated, and the various pattern is produced in the material. It is the characteristic of the material. The characteristic affected on the appearance of the KATANA, so we cannot produce the quite same KATANA. We prepare the four kind of materials for the KATANA (Edge, Side, Ridge and Core). Their hardness is not same.