Fook sau is also another one of the basic techniques in Wing Chun. Along with tan sau and bong sau, it's actually one of the three seed techniques of Wing Chun. What we mean by seed techniques is, most of the hand techniques in wing chun that we use at the beginning level or at the advanced level, especially in chi sau practice, they either relate to bong sau, tan sau or fook sau.
On the topic of fook sau, fook sau is actually basically an idea. It's a concept. The Chinese character itself basically means "to control" or "to cover", and the character is actually a pictogram of a man controlling a dog. Basically, the idea is to subdue or to control. That's basically an idea, so it's not a fixed technique in terms of what it's supposed to look like or what it's supposed to do. It's more of a concept.
Fook sau, when it's practiced in the form, is done a little bit differently than the way we do it when we apply it. When we do the Siu Nim Tao form, one of the main functions is to bring the elbow as far as you can in, so that you stretch the shoulder, and to keep the hand and the wrist bent, and the fingers pointing towards you. Now, the reason why we do this in such an extreme way, especially with the thumb pressing down here to train this tendon here, is primarily for that. We're doing it for strength training in the form.
Not that the Siu Nim Tao form is for training to become brute or powerful, but we need to train the tendons along the arm as long as the muscles on the inside of the forearm, which help to support the way that we punch. We do that primarily by really grinding out the fook sau in the Siu Nim Tao form. However, when you practice a double-arm chi sau or pun sau, it's not necessary to totally buckle down on this, because you don't want to be tense when you're practicing chi sau.
While the form may look like this, when you start to practice chi sau, either single-arm chi sau or later pun sau, your arm and your hand should actually be in a much more relaxed state. If you see that my hand is actually much more relaxed so that I can stick more. One thing you don't want to do with fook sau is to press it down like this, because fook sau is an outside hand and it basically symbolizes the punch coming on the outside of the bridge here.
Since we punch this way in wing chun with a vertical fist, it makes sense that our fook sau still falls in line with that here. If you do the fook sau this way, this actually takes your punch out of alignment, because we don't punch this way in our Wing Chun system. That's why you shouldn't practice fook sau this way here. When you practice in double-arm chi sau, the fook sau should be nice and relaxed on your partner's hands so that if they were to attack you, you can actually feel this one through the hands, either with jum sau or with other techniques, because you have more surface area touching your partner's arm.
This is for chi sau, and then a very simple, practical fighting application is to turn your fook sau flat, this way here, so it's basically just a bridge arm or a covering hand. You can use it in lieu of using a lap sau or a jut sau. If somebody's just standing in front of me and I just want to go in and hit him like this, I only need to create a bridge and punch over here. It's not even necessary for me to grab sometimes. It's even faster to just go over like this. The basic fook sau technique with a punch in the air can look like that. You go here, set up a fook sau, punch over the bridge, drop down, punch, drop down, punch, drop down, punch. That's fook sau for application.