A cog is a type of sailing ship that first appeared in the year 400, and was widely used ever since. Cogs are clinker-built, generally of oak, due to its sturdy nature. This vessel is fitted with a single mast and a square-rigged single sail.
They range from about 15 to 25 meters (49 to 82 ft) in length with a beam of 5 to 8 meters (16 to 26 ft), and the largest cog ships can carry up to about 200 tons.
Used by both civilians and military. It is too small to have a ballista mounted, however it can have archer towers fitted fore and aft on the ship.