Slope aerobatics involves flying aerobatic figures and sequences on the slope with gliders that have been optimized for aerobatic flight. These gliders typically using airfoils that allow identical upright and inverted performance, as well as unique fuselage shapes that permit some amount of sustained knife edge flight. Most gliders feature three axes of control (aileron, elevator, and rudder), and often use flaperons to extend the capabilities of the airfoils for maximum aerobatic performance. Some of the most advanced slope aerobatics gliders feature all-moving elevators and rudders capable of 180* rotation, allowing them to perform "flips" around the pitch or yaw axis, respectively. Airframes are constructed of any material, with wood, fiberglass and/or carbon fiber being preferred for gliders intended for precision aerobatics, and EPP (expanded polypropylene) being popular for low altitude aerobatics where interactions with the ground - like wingtip and/or inverted fin drags, or touch-and-goes off of obstacles - are commonly performed and desired.