Itto-Ryu Rentetsu knives. These exceptional knives are named after the unique cladding material that is used on these san mai blades. This cladding material uses older iron produced over 100 years ago for railroad tracks, anchors, chains, and nails. The refining technology for this material was done in less sophisticated foundries so the iron had many impurities. When we refine this older iron with the latest forging method, the surface yields a unique Mokume type finish which looks a little like wood grain.