Another illegal baseball pitch. This one affects the aerodynamics of the ball directly, unlike the spitball. If you scuff or cut one side of the ball, the rough leather will cause turbulent flow of air (creating lift). You can also polish one side of the ball to drop lift on that side of the ball, or if the umpire never notices, do both for unhittable movement. These pitches are best done by hiding sandpaper in your glove.