you need a tack and a clew line for each reef. On a small sail you can have hooks for the tack, but on a large sail that becomes quite a wrestling match. I have three sheaves at the aft end of the boom, and six at the forward end - three to go up, three to go down. On a standard two line system you will need the ones at the aft end, might get away with only fairleads on the mast at the forward end. But with three reefs I have only 3 lines in the cockpit, not six.