Master Chen Zhonghua Online Lesson on May 11, 2021 - Kelvin Ho
Lean with Back (背折靠)
Right fist and rear kua line up.
Elbow as a handle goes around that line.
Shoulder goes down to the kua.
Kua comes up to the shoulder.
The two lines must be maintained, and they must interact with each other.
The freer the rest of the body with those two lines maintained, the more power there is.
Source: https://practicalmethod.com/?p=75674