Simultaneous Attack and Defence
In Wing-Chun training, both arms are used to block and strike in one movement (Lin-Siu-Dai-Da). This allows for fast counter attacks, compared to the conventional block with one hand followed by a counterpunch with the other.
A Wing-Chun practitioner should be able to block, punch and kick (Wing-Chun 3rd punch) at the same time, thereby confusing his opponent. He can apply many combinations of punches and kicks, so that his attack will be difficult to predict and to defend. His opponent cannot hope that punch X will always be thrown together with kick Y, as any punch can be used with any kick. Even the arms are trained to move independently of each other. This is one of the purposes of the Siu-Lim-Tao.