The larger rods get forged down into sizes that can be laminated to the sides of high-carbon cores to make a type of steel that has been around for centuries and that the Japanese call "san mai." This is basically a method of forge-welding iron and steel together. Some claim that this improves the performance of the blade, but I believe it is mostly a conservation technique. Making steel was extremely time consuming and expensive when manual labor, charcoal production and other variables were factored in. Low-carbon iron (wrought iron) was more abundant and less expensive, so making a blade in this manner was essentially pragmatic. The iron could be placed on the spine and the high-carbon steel could be left for the edge.
I like to do it because it adds "story" to the blade and it's beautiful. A lot of the lower-quality wrought iron was made with techniques that have been around since the early Iron Age, and these methods result in iron of a very heterogeneous nature. The imperfections inherent in the iron appear as complex patterns when etched in acid (see photo above). I love this character. The pattern is even more dramatic when contaminants such as phosphorus are present, as is the case with the iron from this old grain elevator. I also like to use this iron for the guards and other metal fittings in my knives, swords and axes (see photo below).
This iron can also be forged down into flat bars to be carburized into blister steel and shear steel. This is another ancient technique, and it makes functional and beautiful blades. I've also forged the wrought iron directly into knives and spears and carburized them as nearly finished blades in a charcoal forge fire -- a technique once used by the Vikings. You can check out Scott's blog at http://www.bigrockforge.com/blog/