Paak Sau means Slapping Hand. It is one of the most common and useful techniques in Wing Chun and so we must know how to do it and also how to use it. If our opponent attacks with a fist, we will use Paak Sau to slap his forearm, just above the wrist. It can be inside or outside his arm.
Wing Chun principles tell us to use less energy against our opponent and not use force against force. So if somebody punches at us, the best would be to avoid it, but if a punch is coming directly at our face, then we can use the Paak Sau to deflect it and at the same time step back and to the side a little. This is the best way to keep a safe distance from the opponent, but close enough to attack when we want to. When we finish Paak Sau we must keep the palm in Wu Sau 護手 in front of our centreline but some distance away from our face and chest. Being secure is most important. In fighting, security comes first. It is not about winning or attacking first. Being safe is first and attacking comes second. Then we can win without injury. Paak Sau can come from Wu Sau,Taan Sau 攤手 or in fact almost any other Wing Chun hand.
When we use Paak Sau we must relax first. Then when our palm is close to the opponent’s arm, we sharply move the wrist inwards to create the sudden, slapping power to move the opponent’s hand away. Then we keep palm in Wu Sau. If we want to attack afterwards, it is up to us. If you can stay relaxed all the entire time, the more effective your Paak Sau will be.