Knife Edge Flight is fairly simple for the intermediate pilot to acomplish. To do this, roll the airplane 90 degrees, with the wingtips perpendicular to the ground. While rolling into this position, apply opposite rudder to keep the nose high and the plane flying level. You may need to add power, depending on the type of airplane. You may also find that you need to add more rudder throw to your setup and/or use high rudder rate. Use the elevator for steering to keep the aircraft flying straight. Once you've mastered this, you can use the elevator to perform a knife edge figure "8". This is a really neat maneuver, but takes a bit of practice to master. Be sure to make your first attempts with plenty of altitude to recover!