To defend the center-line on the indoor area, you must keep your elbow in on all movements at the center-line. The photo is the double poon sau pose. Chi sau consists of tan sau (palm up hand), bong sau (wing arm) and fook sau (wrist on hand). The answer lies within the Siu Nim Tau form. When you bring your fook sau slowly from just in front of your chest on the centerline and out toward your imaginary opponent, the first part of your fook sau is your hand and wrist. If your chi sau partner can get their punch this far, you can catch their centerline attack. This is a defense, but it could turn into your palm strike or punch! If you can stick to the attacker’s arm at the wrist, you have caught it early and you have a chance to deflect it with your own punch or palm strike or to feel which direction the power is headed, whether it is slow or weak, etc. Feeling this, your reaction must be real time, not “you punch, I defend” type of reaction! This is, of course, the purpose of sticking, speeding up your time to react to attack. If you caught it just a tiny bit late, you must turn to borrow the force of his attack using a jum sau (sinking arm or downward gum sau (pinning hand). These defenses should always be used at-the-same-time as a punch or palm.
The centerline position of Wing Tsun’s arms are a time-gauged defense as deep as the punch that is coming. You can vitually defend, even if the attack coming in close. How far inside your arms is the attack? The sooner you can catch it, the better. If your arm (punch or palm) is not on the centerline, it cannot catch an attack the occurs on the centerline. A skillful attacker will slip in over and over.
Sifu Keith Sonnenberg