Sail. Sails are generally made of flax and hemp, but jute, cotton and linen are also used, while savages make them of matting and vegetable fibers. Sails are stretched by means of masts, yards, booms, gaffs and ropes. A vessel of shallow draught or of narrow beam can bear little sail, while a vessel of deep draught and heavily ballasted, as a yacht, or a vessel of great breadth of beam can carry large sail. A sail acts with greatest power when the wind is right astern, but it can be applied with less strength when on either beam. In the latter case the force of the wind is divided into two parts, one part tending to make the ship go forward, the other tending to make it go sideways, but from the shape of the vessel this second force causes little motion; any that it does cause is called leeway. The sails which are set square across the ship are nearly square in shape, and are called square sails. But many which are set parallel with the keel, called fore-and-aft sails, are also four-sided. Others are three-sided, as stay-sails, which are suspended from the ropes which stay the masts. The larger sailing-vessels usually carry both fore-and-aft and square sails. The schooner has mainly fore-and-aft sails. The brig is mainly square-rigged, and the brigantine is a cross between the brig and the schooner. The cutter is a fore-and-aft one-master. The ordinary sails are mentioned under Yacht.