What is Sunobe in Japanese Katana terminology?

"素延べ" (Sunobe) refers to the first stage of sword making, where the shape of the sword is initially formed. In this process, the iron is heated in a furnace and then forged and extended into a flat rod shape. This is done while the iron is still hot and malleable, allowing the swordsmith to create the general shape of the sword. This stage is crucial as it sets the foundation for the subsequent stages of sword making, including the detailed shaping and sharpening of the blade.