Always keep in mind that what you are developing every time you train are the principles. All of the principles are linked together and are always adjusting together. So AZ Wing Chun Principles: Structure, Position, Distance, Timing, Power, Control, The Tao, Balance, Body Unity, Target, Neutralize, Mindfulness, Fierceness. Target -
Mother-line (vertical) = Central axis of rotation of the body from the top of the head to the groin.
Center-line = The line (vertical plane) from your mother-line to your opponents mother-line.
Controlling target = Your opponents Center of gravity (COG).
Striking target area = Primary target - On your opponents center-line. Secondary target - Off the center line (arm or leg).
Attack-line = The precise target on your opponent (primary or secondary) that is attacked (or manipulated) at the appropriate time.
The Primary striking target area is on the center-line of your opponent. This target is not a spot or a thin line, it is the central core or axis of rotation of the opponents body, from the top of their head to their groin, and can be viewed 360 degrees all the way around their body. Again, Not the front of their body, but the Center of their body. The controlling target or center of gravity (COG) is located on this central core just below the navel (tan tien). This is one very important aspect of what you are learning to feel and connect to in chi sau motion and drills. Know your own COG and your opponents COG.
Your Primary striking target is somewhere on the center-line, but while in motion it constantly changes depending on the situation moment to moment. While you and your opponent are in motion, you can not plan where your attack line will be, but rather you must always be feeling and sensing where the attack line is moment by moment. Secondary targets such as an arm or leg are located off the center line. These targets are used for breaking and joint locking and should ultimately be utilized to get back to and control and destroy your primary target on the center-line.
It is very important to understand that in Wing Chun training we develop the basic concept of one hand controlling while the other hand simultaneously attacks. The controlling hand is not just controlling what it is touching, the opponents arm for example. The controlling hand is controlling the opponents COG, THROUGH the touching point of contact. You are not just trying to control the point of contact. As an example of this function in every day life, if you are writing on a piece of paper with a pencil with your right hand, your left hand needs to be controlling the paper firm to the table in order for the right hand to be able write. The foundation of this skill is developed during basic chi sau rolling motion. During the basic roll there is no attacking and both hands are solely working on developing the controlling function through the points of contact (controlling edge/cutting edge). Later on, attacks are introduced so the controlling function and attacking function can be developed together. This is one reason why chi sau is such a vitally important training drill for correct wing chun development.
The Mind on target - Your mental intent stays sharply focused on your target and on what you are doing.
The Body on target - Your structure and position should always engage the controlling target (opponents COG) whether touching through the controlling edge /cutting edge (beginning level) or not touching (advanced level).
You must understand the difference between the “Controlling Target” and the “Attack target”. They are not the same thing.
Your physical intent always remains either to or from your controlling target, whether you have the attack line or not. There are often many attack line options at any given moment. We will go over this more in depth at a later date.
To make your opponent “stick to you”, you must understand how to properly adjust your positioning to maintain your structure to your target, and always adjusting to fill the gap.
Never chase hands (or legs).
Don't go around the attack line or blocking line. The most direct path to the target is best.
Staying on target correctly is one of many skills that enables you to feel and sense how and when to keep or regain your attack line by adjusting smoothly and automatically without using force and with the best possible timing and leverage.
Even when practicing solo drills and forms, you must always have an imaginary target to focus your intent on.
~ Sifu Carina and Sifu Jim - Southern Arizona Wing Chun Gung Fu