Ship's canvas is a term used to describe the sails of a ship. It is made up of two parts: the SAIL and the plain SAIL. The SAIL is a large piece of fabric that is attached to the mast of the ship and is used to catch the wind and propel the ship forward. The plain SAIL is a smaller piece of fabric that is attached to the boom and is used to provide additional propulsion. Together, these two pieces of fabric make up the ship's canvas and are essential for the ship to move through the water.