A ratchet socket wrench consists of a handle, a 90-degree ratchet end, and a set of cylindrical sockets. If the ratchet is reversible, you can set it to either tighten or loosen the nut. If not, you just place it in the appropriate position to do either. Choose the right socket size, then attach it to the ratchet. The socket fits onto the ratchet through a square nub, which holds it in place while you turn the handle.