This work endeavours to unravel the mysteries of the evolution of a vital piece of seafaring equipment, the rudder. In the process is answers questions on why some technologies develop and endure, while others are soon replaced. The examination begins in the Roman period and from there traces rudder development through the Middle Ages to the age of exploratory navigation. The book offers an analysis of the mechanics of the various rudder systems while never losing sight of the human interest that attends the radical changes brought about by innovation.