As a long time student, I have come to appreciate the subtlety of the six sealing exercise. This mechanic is what produces forward power while the torso is not moving.
Master Chen told us a variation where you can practice this foundation with moving step. e.g step forward then do the move, or step backward before hand.
For those who has seen the two cup gears illustration, this connection is the power behind six sealing four closing. It is unintuitive because the torso has to rotate the opposite way, and require shoulder to be open (which takes a long time to develop)
There are three videos coming up that explain this move in more detail.
“Six Sealing Four Closing Detail 1 ”
“Six Sealing Four Closing Detail 2 ”
“Six Sealing Four Closing Detail 3 ”