My 1981 27' Cherubini has a boom with two lines running through it. One line has a metal hook on it at the end of the boom and it's obvious that line is for hooking into the reef cringle. But what is the other line for? It just terminates in a knot and its use is a mystery to me. Both lines exit from the boom near the mast where they pass through a sheave and a line stopper.