A rudder is a flat, vertical plate or board device that is typically mounted at the stern of a boat or ship and utilized for steering and maneuvering. It functions by redirecting water flow streaming past the vessel, thus influencing the vessel's course or direction. Its operation often involves pivoting it back and forth to manipulate the aerodynamic flow and induce movement or change of direction, either manually or through a steering system. This critical navigational tool allows the vessel to maintain control and stability, especially during challenging weather conditions or strong currents.

1. During their sailing trip, the experienced sailor quickly adjusted the rudder to avoid a large rock in the water. 2. The captain checked the rudder before setting out for the day to ensure that the steering system would work perfectly throughout the journey. 3. Their fishing boat had a large, wooden rudder that had been carefully crafted to provide maximum steering capability. 4. Because the rudder's alignment was off, the crew found it more difficult to steer the yacht in the desired direction. 5. The functionality of a rudder is critical when navigating through the winding channels, allowing the boat to move efficiently against the current.

Rudders, which are vertical plates or boards used for steering a boat, actually have a fascinating history that dates back to approximately 2,000 BC. Original versions can be traced to Ancient Egyptians and other early civilizations, who manipulated oars mounted on the stern of their boats for a steering effect similar to what a rudder does today. It wasn't until around the 12th century that the modern, centered stern rudder as we understand it now became popular, largely thanks to its adoption by European sailors. This new rudder was tied to a tiller and allowed for more precise steering, which in turn enabled more substantial sea exploration and trade, laying the groundwork for the age of exploration. Furthermore, some types of rudders known as "balanced rudders" are designed such that a portion of the rudder remains forward of the hinge, making turning the rudder easier due to the distribution of pressure. This ingenious use of design highlights the blend of engineering, physics, and maritime needs in the evolution of naval technology.