Closed wait

A closed wait, called kanchan in Japanese Riichi, is a gap in the middle of a potential run that can only be filled by one specific tile. You hold the outer two tiles, such as 3s and 5s, and need the single rank between them, the 4s, to complete the set. The two ends are fixed, so unlike a two-sided wait there is no second tile that helps.

Because only one rank completes the run, a closed wait accepts a maximum of four tiles, and fewer if any are already discarded or melded. This puts it on par with the edge wait and well below the eight-tile potential of a two-sided shape like 6p-7p. Players often look to upgrade out of a closed wait when their draws allow, since the narrow acceptance lowers the odds of finishing in time.

In Riichi the closed wait is worth 2 fu, the same as edge and pair waits, reflecting its difficulty. That bonus can nudge a borderline hand up a fu step, and the closed wait is sometimes deliberately kept to satisfy the pinfu-incompatible scoring or to set up a specific dora-bearing tile. Furiten applies as usual: if the middle tile you need is in your own discards, ron is forbidden and you must self-draw it.

Across Chinese, Hong Kong, and Taiwanese mahjong the kanchan shape exists identically, used to judge how live a tenpai hand is, but only Riichi formalizes the fu reward and the furiten restriction. A common example is holding 3m and 5m and waiting on 4m, a wait many players keep when the 4m is a red five or sits next to the dora indicator and so carries extra value.