Question: If I am playing a Concealed Hand, do I also have to pick my own Mah Jongg tile or can I call someone else’s discard?

The letter “C” next to a hand means the hand must remain concealed, so you may not call tiles to make exposures during the game.

However, there is one important exception:
You may call a discarded tile if it completes your hand for Mah Jongg.

✔️ In other words:

• You cannot call tiles and expose during the game
• But you can call the final tile to go Mah Jongg

Source: Mah Jongg Made Easy 2024, p. 15