Question: Can I call a player’s hand dead if they hold a tile in their hand, place them vertically where exposures go, or on their card?

Answer: As per the the National Mah Jongg League (NMJL), players must have 13 tiles in or on their rack at all times. If a player is holding a tile in their hand, or stands tiles up vertically on their card or on top of the exposure area, this results in too few tiles. According to the NMJL, having insufficient tiles is grounds to declare a player’s hand dead. In tournament play, Tournament Directors often enforce the NMJL rule strictly, requiring adherence to avoid a hand being declared dead.

Source: Mah Jongg Made Easy, 2024 pg. 16, RULES AND PENALTIES, #1