What is Jumonji Kita in Japanese Katana terminology?

The term "十文字鍛え" (Jumonji Kita) refers to a method used during the forging process, where the steel is repeatedly folded and forged in two directions, vertically and horizontally. This technique is often employed when creating a cross or 'X' pattern in the steel, which is where the term "Jumonji" (cross) comes from. This method not only helps to remove impurities and distribute carbon content evenly throughout the steel, but also contributes to the strength and flexibility of the final product. The repeated folding and forging process is a crucial part of the traditional Japanese sword-making craft.