Middle finger: leading the energy
Index finger: issuing the power
Put together, it is exactly a screw. The inside is straight, doesn’t move and only hold the pressure, and the outside thread rotates to create power. The screw itself is easy to understand and use. It is difficult to gain the function of the screw through practice with the middle and index finger.
Once we figure out this set of relationship, we can use it as a reference and apply it to the body.
The so-called train to have a stick is referring to the middle finger, which is the column in the screw, and the so-called train to have a rope is referring to the index finger, which is the thread of the screw.
It will be clearer with the diagram below.
The stick in the middle is the middle finger, the arm, the leg, the central axis, the front axis, and the rear axis.
The ropes on it are our muscles, skin, tendons, ligaments, and so on.
We rotate the stick inside through the movement of the ropes, which is learning and practicing.
We rotate the stick (shaft) on the inside to drive the rope (limbs) on the outside, which is gaining and using gong fu.