The term 'Nautical Steering Device' refers to two devices used in the navigation of ships and boats. The first device is a TILLER, which is a lever used to control the RUDDER of a boat or ship. The second device is a RUDDER, which is a flat plate or fin attached to the stern of a boat or ship that is used to steer the vessel. Both the TILLER and RUDDER are essential components of a nautical steering system, allowing the captain to control the direction of the vessel.