The myrid other jings, all are just different uses of sticking jing. Sticking a result of being sung and soft with sensitivity. Like sticky things, like a stamp stuck on an envelope, causing myself to stick to my opponent, in not letting go and not resisting, listening to his jing, this is the reality of nien jing. Sticking is the method for understanding completely your opponent's condition. When you can stick, then you can fully utilise sensitivity's agile characteristic.
Agility comes from sung and comes when one is calm and quiet.
Not being light means not being able to be sung, this skill is all from practicing the boxing form. Boxing theory is from nature and is so made complete, we need to express it completely when doing the form. The postures in the form have high and low, every person's sung and softness level is different, so sticking jing's sensitivity will come according to each person differently. A little more advanced, when you can lighten it, the bones will no longer be in contact, you can only feel the flesh being in contact. High level sticking, the contact is only on the skin surface.