East begins by discarding, face up, naming the tile aloud as it is placed. From there, each turn offers a choice.
| You may | What happens |
|---|
| Draw from the wall | Take the next tile, then discard one. The ordinary turn. |
| Call the discard | Claim the tile just discarded, if it completes a Pung, Kong or Quint you can show. Say “call” before the next player draws. |
| Call for Mah Jongg | Claim the discard because it completes your whole hand. Any player may call, in or out of turn. |
Exposing. When you call a discard for a grouping, you place that grouping face up on top of your rack, then discard. It stays there for the rest of the hand: you have told the table what you are building, and you have committed to it. The exposure cannot be broken up or rearranged afterwards.
Redeeming a Joker. If an exposure contains a Joker, yours or anyone else’s, and you hold the real tile it stands for, you may swap them on your turn and keep the Joker. A Joker sitting in a discard pile is dead and cannot be claimed by anyone.
If the wall runs out before anyone wins, the hand is a wall game. No one scores and the deal passes on.