Pretty simple, but effective – this drill helps teach the round off technique. It puts emphasis on kicking over the top and on squaring off to land with both hips on the pacman (at the same time, ideally!).
You can see on her first attempt the gymnast in the video was too slow – not enough kick over the top and too slow in squaring off — all causing her to bounce off to the side!
This is important to correct from the get-go so that you don’t get crooked tumblers once back handsprings are added on!