Steel square bars are solid metal bars with a square cross-section, available in carbon, stainless, alloy, and weathering steel. Sizes range from 6 mm to 300 mm in width and 6 to 20 feet in length. They come in hot-rolled, cold-drawn, and pickled finishes, with options like galvanization and powder coating. Common standards include ASTM A36, A572, and A240.