The sails are divided into square sails and fore and aft sails. Of the former, the lowest sail on the main mast is the main sail or main course, then come the lower and upper topsails which are both attached to the topmast. Higher still is the topgallant sail and above this lie the royal and the skysail. Next comes the moonraker but we can disregard this one as it is not always necessary. The sails on the other two masts are classified in exactly the same way, with the name of the mast prefixed