Belt drives transmit power between two or more rotating shafts, usually with parallel axes of rotation. The belts are looped over pulleys attached to the driver and follower shafts. The pulleys are placed at a measured distance to create tension on the belt. The friction causes the belt to grip the pulley when in operation. The rotation of the driver pulley increases the tension on one side of the belt, creating a tight side. This tight side applies a tangential force to the follower pulley. Torque is then applied to the driven shaft. Opposite the tight side is the slack side, where the belt experiences less tension.