During the Spring workshop here in Arizona, my Sifu, Master Sam F.S. Chin spent time covering the concept of "completing the loop" in some detail. The following clip is probably the clearest example of the concept of the loop and the interrelated concept of "every circle having a cross" we have on video.

The idea is that you must pass the "energy" or vector of force past each of the cardinal points on the circle before your loop can be complete. Why is this important? Well in the words of my senior brother Alex (Chief Instructor of Russia), "it's like when a fish swallows the hook completely". It's the application of force not just at the point of contact with the opponent, but it's as if you're pulling from their feet directly.

For reference, here is a clear picture of the diagram that my Sifu is referring to in the video.