horizon m/s describes the sail of an preposition
gaff_topsail is fore_and_aft_sail. fore_and_aft_sail is sail. fore_and_aft_sail is not sail. head_sail is not sail. balloon_sail is sail. press_of_sail is not sail. sail is structure. press_of_sail is sail. gaff_topsail is not fore_and_aft_sail. head_sail is sail.