Reefing Lines, Not All
I agree: that long line is fed up, through the grommet in the sail, down to the other side, through a block, then forward to a cleat midway along the boom. It's a reefing line. Those small lines hanging down from each side of the sail are for keeping the excess sail out of the way only: they are not meant to take the load of a reefed sail. If they are tied tightly, the small, un-reinforced grommets they pass through will tear out, necessitating a costly repair. The reef is held by the front and back reefing lines; those other house-keeping lines should be tied LOOSELY, or not at all, or you're asking for a torn sail. Reefing is normally accomplished in 5 basic steps, depending on the type of reefing system you have: 1) Ease main halyard enough to 2) Pull down the forward (luff) of the mainsail & secure the large grommet using a hook on the mast or a dedicated reefing line 3) Pull down the rear (leech) of the sail with your mystery line, correctly reeved through the sail/boom block. 4) Re-tension main halyard 5) clean up the loose bunting of the mainsail Taking out the reef is accomplished by reversing the steps. The first rule of reefing is: the first time you ask yourself if it's time to reef, it's already past time. Do it now. Becoming familiar with how your reefing system works, & practicing in light weather will mean you'll be ready to reduce sail quickly and efficiently when the need arises later: and it will. Fair Winds, Jeff
