>Chapter 19
>When you have two middle tile pairs, kill one

>Closed hand iishanten with two pairs

>When you have yakuhai, toitoi, honitsu or the like, pairs of honours or 19m are excellent blocks. But when your hand cannot be opened, they are weak. Let's look at different blocks and how many tiles can change them or turn them into complete groups:
TN: The "=" will tell us how many tiles complete the block, the next line (if present) will talk about possible changes (improvements).

>Honour / manzu pair = 2 tiles

>Other terminal pair = 2 tiles
>Drawing 23/78 also makes it a kanchan with pair, letting the block accept 6 tiles total.

>2/8 pair = 2 tiles
>Can also gain kanchan acceptance as above, or draw 1 kind of tile for a ryanmen with pair shape (e.g. 223) accepting 10 tiles.
TN: Note that "1 kind of tile" and "X number of tiles" are not the same thing. 1 kind of tile in this case is just 4 tiles. Why is Owata like this

>4/5/6 pair = 2 tiles
>2 kinds of tiles for ryanmen with pair shape as above.

>3/7 pair = 2 tiles
>As above, but one of the ryanmen possibilities is an A-class ryanmen (i.e. 1-4 or 6-9).

>Penchan = 4 tiles

>Kanchan waiting on 2/3/7/8 = 4 tiles
>1 kind of tile to change to ryanmen.

>Kanchan waiting on 4/5/6 = 4 tiles
>2 kinds of tiles to change to ryanmen.

>Ryankan 135/579 = 8 tiles
>1 kind of tile to change to ryanmen. Worse than ryanmen because it uses 3 tiles rather than 2.

>Ryankan 246/468 = 8 tiles
>1 kind of tile to change to ryanmen, but can accept red fives and works with tanyao.

>Ryankan 357 = 8 tiles
>2 kinds to change to ryanmen.

>Ryanmen 3-6 or 4-7 = 8 tiles
>The tiles waited on are easy to use, so can be hard to win with.

>Ryanmen 2-5 or 5-8 = 8 tiles
>It's easier for 2 or 8 to come out. Also accepts aka, making it good for both value and defence.

>Ryanmen 1-4 or 6-9 = 8 tiles
>It's much easier to win on 1 or 9.