Open hand

An open (or exposed) hand is one in which the player has claimed at least one meld from another player's discard — by calling chi to complete a run, pon for a triplet, or an open kan — and laid those tiles face-up beside their rack for all to see. Once any such call is made the hand is permanently open for that deal; the only exception is a concealed kan formed from four self-drawn tiles, which does not break concealment.

Opening a hand trades scoring value and certain restrictions for speed and reach. In Japanese Riichi this trade-off is severe: an open hand cannot declare riichi and loses access to closed-only yaku such as pinfu and iipeikou, and many remaining yaku suffer a 1-han penalty (kuisagari) when open — sanshoku and ittsuu drop from 2 han to 1, for example. Crucially, an open hand must still contain a yaku to win at all, which is why players open primarily on yakuhai, tanyao, or honitsu shapes that survive being exposed. In Hong Kong and Chinese rules opening is far less punishing, so calling tiles to assemble pungs and flushes is routine.

The strategic appeal is tempo: an open player can snatch exactly the tile they need from the table rather than waiting to draw it. For example, holding 2z2z (a value wind) and pon-ing the third 2z instantly establishes a yaku and accelerates the hand. A common beginner error in Riichi is opening a hand that has no yaku source, leaving it formally complete in shape but impossible to declare a win on — a 'dead' open hand. Knowing which calls keep a winning path open is essential to playing exposed hands well.