on cruising yachts, and nearly all racing sailboats, the jib needs to be worked when tacking. on these yachts, there are two sheets (ropes) attached to the clew of the jib. as the yacht comes head to wind during a tack, the active sheet is released. at the same time the other sheet (the "lazy sheet") on the other side of the boat is pulled in. this sheet becomes the new "active sheet" until the next tack.