There are many different variations of this move, it is basically a bridge with your feet not touching the floor. it can be done from a handstand, headstand, or on your elbows. once your balanced vertically with your feet straight up, you begin to arch your back and lower your feet down as if you were doing a bridge, putting your chin to your chest will help with balance. the more you back is arched the better it will look. this is a good freeze, and can be linked with moves such as 90's, I have also seen it done with rubber bands.