is an important principle of the Chen Style Taijiquan Practical Method. The allows the vertical stretch of the body to take place. This creates two lines in the body: 1) left foot vertical line. 2) right foot vertical line.
The other lines in the body from similar actions are: 3) left hand-right hand stretched horizontal line. 4) left foot-right hand stretched 45 degree line. 5) right foot-left hand stretched 45 degree line.
These five major lines in the body maintain the(掤）energy in the body. They also contribute to the concept of “five points struggle out”, 五点外挣。