1. The square sail on a keeled ship, (for example a Greco Roman merchantman) can give an angle of 67.5º (6 points) to the line of the wind when fully trimmed and tacking into the wind. The keel provides resistance to the sideward force of the wind.
2. A square rig with the help of some fore-and-aft lateen (mizzen) sails as used on European sailing ships from the 15th century to the 19th century allows a 56.25º (5 points) to be obtained. An Arab lateen rig gives the same angle when close-hauled but since a greater area of sail catches the wind, it sails more swiftly and efficiently.
3. A well-designed Arab lateen could come within 4 points of the wind. One can see why Nabataean and other Arab sailors would desire such a boat for pirate activity against the Greeks and Romans.
4. The most efficient design of sail for utilizing a head wind is the complete fore-and-aft rig of a modern yacht. It can usually come within 4 points of the wind, and sometimes even achieves 3.