at sea, is a term used by the steer'sman, when the main-fall, fore-fall, or sprit-fall, hinders his seeing to steer by a land-mark; upon which he calls out, "Duckup the clew-lines of these sails;" that is, hale the sails out of the way. Also when a shot is made by a chase-piece, if the clew of the sprit-sail hinders the sight, they call out, "Duckup," &c.