China's rudder design
But it was the chinese under the han dynasty that added a crucial technological development that advanced ship design. During the 1st century AD,they invented the wooden rudder which was used for steering. A rudder is basically a flat sheet of wood,used for steering that is connected to a boat via a hinge(or pivot). Cables connect to the rudder,pushing or pulling it to the left or right,thereby turning the ship. The stern-mounted rudder replaced the oar steering system as it required less manpower and didn't interfere with the operation of sails