Question: what is the difference between a universal beam and an rsj?
Answer: Just to confuse you a bit more, BS4 (the British Standard for Structural Sections) lists UBs (Universal Beams), UCs (Universal Columns), and Joists. RSJ stands for Rolled Steel Joist. All of the above are rolled steel sections, but only one of them is a joist. You can also get welded sections and cold formed sections.