An aileron is an aircraft control surface used to control roll. They are found on the trailing edge of each wing, and can be deflected up or down to reduce or create lift to induce the roll motion along the longitudinal axis. Ailerons are used in opposing pairs to accomplish their task. To roll the plane to the left, for instance, the left aileron is raised which slightly reduces lift for the left wing. Simultaneously, the aileron on the right wing is lowered, which creates slightly more lift for the right wing. The combined effect lowers the left wing while raising the right wing, thus causing the entire aircraft to roll to the left.