Ball Nutz is a type of Active Protection.
Ball Nutz can be seen as an active nut (Ball Nutz by Trango seen on the right). Ball Nutz are placed by pulling the trigger bringing the 'ball' into the notch (lowering the overall profile of the Ball Nutz). The ball nut is placed into a thin crack and the trigger is released. This causes the ball to be pressed out against the rock (widening the profile of the ball nut). Due to the friction of the ball on the rock when the piece is weighted it will try to 'expand' and therefore jam in the crack. Ball Nutz can be used in parallel cracks.
Ball Nutz are designed to protect small to medium sized cracks. Ball Nutz are generally not needed on a beginner's rack.