The steel used in the Japanese Katana was a complex mixture of the minerals and materials found throughout the land. The blade itself actually contained four distinct types of metal: back metal, side metal, core metal and, probably the most fascinating of all, the edge metal. These metals were then integrated into one masterful creation, and folded over each other anywhere from one hundred to one thousand times.

Some mythical and theatrical account, such as the renowned creations of fictional sword maker Hattori Hanzo, were said to have been folded well over two-thousand times. Regardless of the historical truth of the existence of such blades one thing can be known; with each subsequent fold the samurai katana became exponentially stronger and more deadly.