The rota was a cylinder, open on one side, that was built inside a wall of a monastery; it was used for exchanging mail and food with cloistered clergy, being their only communication with the world. It was usually about 50 centimeters wide by 30 centimeters high, and its opening did not permit visual or tactile contact with the uncloistered. Messages or food were put into the cylinder, then the rota was revolved so that the opening faced the other side.