One of the original names for Taiji is Shi San Shi – 13 postures. It doesn’t mean there are only 13 postures, but 13 basic ideas. These were the 5 directions (wuxing) and 8 methods (bagua).
In the so called 8 basic methods (people also call them 8 basic jins), Pen, Lu, Ji, An are called Si Zheng (4 main directions – N, S, E, W), and Cai, Lie, Zhou, Kao are called Si Yu (4 diagonal directions – NE, SE, SW, NW). This is actually not part of intellectual (word/numerology) game you see a lot in internal martial art that doesn’t mean much. By mapping those techniques to those directions, it indicate both their overall importance and their relative importance to each other.
Peng Lu Ji An are called the “4 cardinal directions” because they are the four main methods, Cai Lie Zhou Kao are the corner directions because they are supplemental/assisting methods. That means a lot of times in real fighting, in order to execute Peng Lu Ji An, you need to employ Cai Lie Zhou Kao to help. In many cases this is necessary because of less than ideal timing and distance.
For example, you reaction was a little slow, the opponent got way too close, too fast, you can use some type of elbow or shoulder strike to open up a little breathing room (both space and time) in order to properly execute one or more of the 4 main methods.
Another example is when someone grabs us, if our reaction is a little slow, the grab on the wrist already very strong, very solid, making it difficult for us to move, we execute a quick, short, explosive (shaking/shuddering type) jin to loosen his grip a little first, before proceeding to the regular/main technique we want to use. Short distance but powerful, that’s the type of jin Cai Lie Zhou Kao produce right?
In this context, the idea is not to get your opponent directly with those techniques. Even if they miss, if the opponent reacted by moving away, it served its purpose. In internal martial art we don’t just directly attack someone with powerful strikes hoping they would land. We always try to control him first. So of course if you got control of his balance already (i.e he is helpless, cannot respond to whatever you’re going to do to him next), you can also use elbow or shoulder strike to finish him.
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