Initially sails provided supplementary power to ships with oars, because the sails were not designed to sail to windward. In the Austronesian Indo-Pacific, sailing ships were equipped with fore-and-aft rigs that made sailing to windward possible. Later square-rigged vessels too were able to sail to windward, and became the standard for European ships through the Age of Discovery when vessels ventured around Africa to India, to the Americas and around the world. Later during this period—in the late 15th century—"ship-rigged" vessels with multiple square sails on each mast appeared and became common for sailing ships.