スジの法則を知らない
スジは相手の攻撃に対する防御はもちろん、序盤の不要牌探しには欠かせない知識。1-4-7はワンセットではなく、1-4と4-7に分かれることも知る必要がある。
以下、海外プレイヤー用
9. One doesn't know a low of wait.
A mahjong player should understand a low of wait. It is useful for the player when he(or she ) builds his hands, and when he wants to avoid discarding another players's winning tile.
A half of all waits is‘open wait’like
, 
, etc.If one player discarded
, it's easy for other players to discard 
and 
.Because he cannot go out by
and if his wait is open wait.So, mahjong players should know a low of wait. All of them are 1-4, 4-7, 2-5, 5-8, 3-6, and 6-9. Mahjong player should not understand them as 1-4-7 that is summarized both 1-4 and 4-7, but should understand them separately.