"San Mai" also known as "three-layer," is a traditional Japanese knife-making technique. In Japanese, "San" means "three," and "Mai" means "layer." This process involves combining three different types of steel, typically sandwiching a hard stainless steel core between two outer layers of softer steel. This method leverages the advantages of different materials: the central hard steel provides a sharp edge and excellent edge retention, while the outer softer steel layers enhance the blade's toughness and durability, as well as making it easier to sharpen and maintain.