Two chapters before introduced quite a number of good shapes in Japanese mahjong that are important but often overlooked, this time I'll introduce some other commonly seen taatsu.
6. Double/Triple middle taatsu
Double/Triple middle taatsu refers to 468, or 2468 etc continuous kanchan type of shape.
Quite a few beginners think of kanchan as a bad shape, and do not like this type of shape. But we have to be aware: a 246 double middle taatsu has the same number of effective tiles as a ryanmen. The difference is that the former require 3 tiles, while the latter only require 2 tiles, the former has a lower efficiency. It may not be a good shape, but when the number of taatsu in your beginning hand is not enough, the double middle taatsu is still useful.
7. 3556 shape
On the surface, the two taatsu of 35 + 56 seems to be similar to the aforementioned 35 + 67, in fact there's a huge difference between them. The reason is that 35, 56 violates the problem of effective tiles overlapping. In this situation, 35 taatsu has a low value, if there's enough taatsu, 35 should be the first to be discarded. Having 56, or 556 remaining should be enough.
8. 5566 shape
Everyone might think of 5566 as two ryanmen, and there's a chance of becoming ippeiko. But to me, it's a bad shape. 5566 definitely has effective tiles overlapping. It might seem easy to draw 47 twice, but when there are other good taatsu, this should be quickly disposed of.
Discussion regarding taatsu stops here. If there are any questions, feel free to ask them. The next chapter will be discussing some examples of problems.