I also am interested in making my own bridge. The bridge needs to be a specific length and I want to model a specific bridge as closely as possible. Where can I find lengths of steel I and H beams in lengths up to 3 feet long? Dimensionally, these need to be 3/8" x 3/8", 3/8" x 1/2" or 5/8" - that order of magnitude. I also prefer steel, tho if steel beams are impossible to find, I'd consider brass. I've only seem smaller sizes than what I need at K&S metals and all these are only 12" long.