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American Mahjong School

Concealed hands & the “C” rule

Every line on the NMJL card ends in an X or a C. X means exposed. C means concealed — and it is one of the most misunderstood letters on the entire card.

Right vs. wrong at a glance

We use real vector tile faces so they stay sharp when enlarged. Below we show only whether Concealed (the C marker) is broken — the exact bonus comes from your current year’s official NMJL card.

✓ Right: never called or exposed a set

Every tile came from your own draws and nothing is exposed on the table — that is a Concealed hand, eligible for the C bonus.

✗ Wrong: called a set mid-game

Once you call a discard and expose a set (e.g. a pung of Green Dragons), the hand is no longer Concealed and the C bonus is lost.

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Concealed hands (the “C” rule)

A concealed hand is built entirely from tiles you draw yourself. You may not call any discards — with one narrow exception. Get this right and the C lines stop being intimidating; get it wrong and your hand is dead the moment you expose a tile.

The rule in one line

C = you may not call any discard. You complete the whole hand by drawing. The only discard you may pick up is the 14th tile when it completes Mah Jongg.

C vs X — the letter beside every line

Every line on the NMJL card carries a letter next to its point value: C or X. That letter tells you how the hand is allowed to be built.

X — exposed

Call freely

  • Call a discard at any time to build a pung, kong or quint
  • Add a called tile to an exposure you already have
  • Declare Mah Jongg on someone’s discard
C — concealed

Draw it yourself

  • Draw every tile off the wall
  • Exchange a joker on your own turn
  • Claim the 14th tile — but only if it wins
  • Call a discard for a pung, kong or quint
  • Expose any part of the hand — that is an immediate dead hand

The National Mah Jongg League is explicit: the 14th tile “may be thrown by another player or picked by the player who is set for Mah Jongg, whether playing an exposed or concealed hand.”

Concealed (C) vs exposed (X) at the rack
S Concealed (C) Exposed (X) Every tile drawn — no discards called. Called sets ride on top of the rack.
In a C hand nothing is exposed; in an X hand, claimed groups sit visibly on top of the rack.

Why concealed hands are valued higher

  • Harder to complete. You depend on your own draws for 13 of your 14 tiles — you give up the free melds you would get by calling other players’ discards.
  • Priced into the card. C lines carry their own, typically higher, point value to reflect that difficulty.
  • Stealth. Your rack stays hidden, so opponents learn almost nothing about what you are building.

In short: you trade speed for stealth and for points.

The dead-hand trap

#SituationIs the C hand still alive?
1You call a discard to make a pung or kongNo — immediate dead hand. A concealed hand may not claim discards.
2You expose a self-made group face-up on your rackNo — any exposure breaks concealment.
3You draw the 4th tile and form a concealed kong from your own handYes — you did not call; keep it as a concealed kong.
4You call the 14th tile to declare Mah JonggYes — this is the one allowed discard.
5You exchange a joker during your turn (after drawing)Yes — joker exchange is allowed and does not expose your hand.

Can you make a kong in a C hand?

  • Yes — a concealed kong. Build it from tiles already in your hand (you draw the 4th yourself, or already hold all four), then take your replacement from the dead wall.
  • No — not by calling. Calling a discard to complete the kong exposes the hand and kills it.

See Kongs & replacement tiles for the full kong rules.

How to play a C hand well

  • Commit early, quietly. A concealed hand gives opponents nothing to read. Let them guess while you build.
  • Watch the wall count. Because you rely on draws, a C hand is more likely to run out of wall. Track how many tiles remain.
  • Keep a fallback line. If your draws go cold, a C line can pivot to an X line only if you have not exposed anything yet. Once exposed, you are locked.
  • Use joker exchange, not exposure. Swapping a natural tile for an exposed joker is legal and keeps you concealed — a great way to improve a C hand without breaking it.
  • Call the winning tile with confidence. The final discard is fair game. Many new players wrongly assume a C hand must be self-drawn; it does not.

Why this page exists

The C marker causes more avoidable dead hands than almost any other single rule. The statements above follow the National Mah Jongg League standard as clarified in MahjLife's commentary on Article 22 (“Claiming a discard when playing a concealed hand”) and the American Mah-Jongg Association's Rules Companion. Where your table or tournament differs, the current official card and that table's house rules always win.