 A small ship with two masts, both fore-and-aft rigged, with the mizzen located well forward of the rudder post and of only slightly smaller size than the mainmast (if the height of the masts were reversed—the taller in the back and the shorter in the front—it would be considered a schooner).If square-rigged on her mainmast above the course, it is called a "square topsail ketch".Historically the mainmast was square-rigged instead of fore-and-aft, but in modern usage only the latter is called a ketch.