Chi sau develops the fighting reflexes of wing chun. Strikes and counters are directed between students, to begin with, in a co-operative manner and a certain order. This is known as look sau. Initially the movements are done from a stationary position, concurring with the sui nim tao period in training. Moves are first done with one hand and then with two.

The movements in wing chun cannot be classified into attack or defence. A single movement can serve either purpose, and at higher levels does so simultaneously. Put simply, a wing chun student will defend against an attack by delivering their own strike back at the opponent, intercepting the incoming strike in the same movement. The practice of sticking hands deals with the moment of contact as the strike is intercepted, and trains the wing chun student to deflect the opponents strike, whilst striking through themselves. The shapes of wing chun and the paths they take, are arranged to provide a structural advantage to the exponent. The correct responses are ingrained through the practice of chi sau.

As one learns the skills of pivoting and stepping in chum kiu, they are applied to chi sau. Students also begin to apply movements randomly, rather than in order. This is developed into a co-operative form of semi-sparring. When practicing chi sau, one should not try to ‘win’, no brute force should be exerted. Effort should be focussed on relaxing and maintaining balance.

Chi sau can be incredible fun when done correctly, and like much of wing chun has an addictive element to those who train it regularly.