Most of the "how" is well explained in posts above. The "why" is a different matter. In high speed fighter jets of the 1950's and later the rudder was not powered assisted in the same way as elevators and ailerons were, thus when the speed got above about 250 knots the rudder started to become in operative due to the force of the air passing over them. In my experience the Hawker Hunter was a good example of this.