Although superficially similar in appearance to the brig or brigantine, the snow is a much older three masted design which evolved from the larger fully rigged ship. The foremast and mainmast are both square-rigged, but the fore and aft rigged spanker sail is attached to a small trysail mast (or in modern times a steel cable) stepped directly behind the mainmast. This "snow-mast" allows the gaff to be raised unhindered by the mainmast and higher than the main yard, which in turn also allows the snow to fly a main course without complications.