The birlinn is clinker-built and could be sailed or rowed. It has a single mast with a square sail.
Smaller vessels of this type have as few as twelve oars, with the larger having as many as forty.
They are used as both transport ships of both personnel and goods as well as combat ships that are mounted with a ballista at the aft of the ship and single archer tower at the fore of the ship.
They are smaller than Galleys
but are larger than Cogs