As I understand it, Chi-Sau is just a method to build sensitivity to energy, so that one can learn how to use another's energy to his advantage. Chi-Sau also works on timing and reflexes. In a real fight, I'm much more inclined to step off the attacker's centerline (moving to the outside gate), while still keeping mine towards him. By applying this footwork, I have the advantage of going straight into chain punches,low line kicks or applying a strong pak-sau to his striking hand or shoulder, thereby "technically" trapping him. If he has the chance to come in with a second hand or foot, then this is where sensitivity to energy becomes important, in that I want to move WITH my opponent's energy, rather that trying to use force against force. As far as trapping is concerned, I would never go into a fight with the intention of trapping. If the opportunity presents itself--great! Wing Chun has many other "tools" to bring to a fight than just trapping!! I'll get off my soapbox now--can I get an "AMEN"??