Cherri, The boom downhaul will keep the gooseneck from popping up out of the sail slot in the mast. If the boom downhaul is not set, you cannot tension the luff of the mainsail with the halyard. After losing a number of sail stops -- overboard, in transit, spirited away by gremlins -- I now use a shock cord sail gasket --WM, page 1046. (Avoid the use of bungee cords on your boat. The hooks tend to snag everything and can cause serious damage to the vessel and injury to the crew.) Insert the gooseneck in the mast slot, run the short downhaul line up through the hole in the gooseneck and back down through the jam cleat below the gooseneck. Wrap a sail gasket around the mast above the boom (but below the slot opening) before inserting the sail slugs. Once the slugs are in the mast slot, slide the sail gasket up to close the opening. I have a large collection of shock cord sail gaskets. I use them all over the boat: to secure the sail to the boom, to keep the mainsail slugs in the mast slot, to secure the jib to the bow pulpit so it won't blow overboard, to lash lines and cables to the mast when trailering, etc. While doing tasks aboard, you can hold them in your teeth, around your arm, around your neck, in the straps on your life jacket... They are really handy. I wouldn't be without a dozen or so at the ready aboard Poco. Joe Kidd M15 #207 "Poco a Poco"