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ID14-Singles and Pairs Must be Self-Picked Unless Ready to Win
Question: Can I call a tile if I am playing a Singles and Pairs hand or a grouping such as NEWS or FF?
Answer: You can never call to expose a single tile, single grouping or a pair unless that discarded tile is the one needed to complete Mah Jongg. As well, all hands under the Singles and Pairs category are concealed hands, and therefore can never be exposed during the game, unless the discarded tile is needed to complete Mah Jongg.
Source: Mah Jongg Made Easy 2024 page 14 para, THE PLAY