The Sun character center punch, is a unique punch (vertical fist) only used in Ving Tsun. Yes, other styles have a similar type of punch, but the uniqueness is not just the physical or mechanical punch but understanding and applying the attributes of the Yat Je Jung Choi.
When applying the Yat Je Jung Choi, the emphases is on the bottom three knuckles.
The reason for the emphases on the bottom three knuckles is for support.
From the photo you can clearly see that the bottom three knuckles are supported by the wrist and forearm. The top knuckle has no support from the wrist. The chances of injury to your fist and wrist are reduced when punching with the Yat Je Jung Choi.
Instead of using a jab, a cross or hook punch like in boxing or street fighting the Ving Tsun fighter wants to ensure that the punch is not just powerful and fast, but it must be supported by the whole body and not just the shoulder.
Which brings us to another idiom: Kuen Yau Sum Fot (The punch comes from the heart.)
This idiom has two significant means:
First it talks about location. The punch travels down the center of the body (center line) and forward, again the Yat Je Jung Choi punch looks strange and at first it feels very weak but with many hours of practice it will be a very useful weapon. This center line is close to the heart and from this location the punch is thrusted forward with the shoulder down and elbow rolled under the arm and not extended outward (elbow out means no power). Some Ving Tsun schools or branches punch until the elbow locks out and the arm is straight. From personal experience, when I punch until the elbow locks out it causes the shoulder muscles to pull the punch off the centerline. To eliminate this, I punch until I feel the shoulder muscles starting to tighten and pull the arm in an upward direction. Granted a straight arm punch with the elbow locked out will give a few extra centimeters in reach but I prefer to stop short of locking out the elbow so as to keep the fist on the center line and I have other reasons that can be explored later.
Secondly it talks about the whole body. When we discussing the heart, it is not only talking about the organ that pumps blood through the body but it talks about you as a person and the body as a whole. When the Ving Tsun fighter must use the fist, it will be supported by the whole body, from the bottom of the foot to the knuckles of your fist it must be supported. This is called whole body Kung Fu. The fist must go forward with purpose and intent.
A third idiom that every Ving Tsun player needs to learn is Kuen Mo Lai Yeung: when using the fist, do not stand on ceremony.
This idiom will be discussed at another time.
In conclusion, the Ving Tsun punch is unique and when applied correctly it is powerful.