Kuikae

Kuikae 「喰い替え」 is a particular restriction applied to tile calls, especially involving chii. It is commonly referred as "swap calling". When a player possesses a completed sequential group, like 4-5-6, then a player has the option of calling on a discarded 7. Upon doing so, it is commonly forbidden then to discard the 4, until the next tile draw.

Examples

Example 1: Chii

1. 
2. Left player discards:
3. Chii is called to form
4. is left over, but cannot be discarded on the same turn.

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Example 2: Pon

1. 
2. Any player discards:
3. Pon is called to form (orientation depending on tile source)
4. is left over, but cannot be discarded on the same turn.

External links

• 喰い替え

Kuikae in Japanese Wikipedia