Cog

The cog is a type of clinker-built cargo sailing ship that emerged in northern Europe around the tenth to twelfth centuries, characterized by a flat bottom, straight stem and sternpost, high freeboard sides, and typically a single large square sail on a central mast. It became the dominant merchant vessel of the Hanseatic League, the medieval trading network of northern European port cities, carrying bulk cargo such as grain, timber, salt and cloth across the Baltic and North Seas, and its cargo capacity and defensible high sides made it well suited to the long-distance bulk trade that underpinned Hanseatic commercial power before it was gradually superseded by the carrack and other later ship designs.