Question: What does the “C” stand for on the card? I often hear players’ ‘say “Concealed Hand” or “Closed Hand”?

Answer: The proper term for the “C” on the card is “concealed or Closed.” When playing a concealed hand, a player may not call a tile to make an exposure (such as a pung, kong, or quint).

However, there is one exception:
When the hand is complete except for one tile, a player may call a discarded tile to declare Mah Jongg.

✔️ In short:

• No calling to build the hand
• Calling is allowed only to win

Resource: Mah Jongg Made Easy 2024, p. 12