Christopher Columbus' ships did not use rudders in the traditional sense. Instead, they used a steering oar or a "quarter-rudder" mounted on one side of the ship at the stern, which was controlled by ropes from the deck. This type of steering mechanism was common in Mediterranean and Atlantic European ships of that era.
A true stern-mounted rudder, pivoted on hinges and controlled by a wheel or tiller, was not in widespread use until the 14th century and became more prevalent in the 15th and 16th centuries. Columbus' ships, which set sail in 1492, predate the widespread adoption of the stern-mounted rudder.