Final answer:
The rudder-like protrusion's main function is to control the direction of movement and to enhance maneuverability, which was particularly significant in historical ships like the caravel.
Step-by-step explanation:
The function of the rudder-like protrusion on ships, such as the caravel, is primarily to control the direction of movement and to enhance maneuverability.
During the Age of Exploration, advancements in ship design, including the positioning of the rudder at the stern, significantly improved a vessel's steering capabilities. This design change, in conjunction with the addition of the lateen sail, allowed ships to sail more effectively into the wind through a process known as "tacking." The rudder's essential role in navigation illustrates the connection between shipbuilding technology and the ability to journey across greater distances at sea.