|Tile types waiting||3 sided wait|
|Tiles available||11 tiles|
Sanmenchan 「三面張」 is a class of wait patterns for three-sided waits. The most common involves a combination of two ryanmen (open wait). In fact, this is the default form. This pattern utilizes a string of five consecutive numbered tiles in the hand. The exact middle tile of this string is one of the waiting tiles, while the other two hand off the edge of the string. Hands can wait on three kinds of tiles using other forms. Some of them take names of their own, while others do not.
This pattern consists of five consecutive tiles (that do not include 1 or 9): two ryanmen connected by one mutual waiting tile in the middle. The three-sided waits generated from this pattern are the most common form of the three-sided wait; when the term sanmenchan is used on its own, it is often in reference to this pattern of wait. The wait always points to one of the full suji patterns.
This pattern is a powerful wait due to the large number of waiting tiles: 11 maximum possible, using any of 3-tile types. That number cannot be 12, due to one waiting tile (the middle number) already present in the hand. The waiting pattern is limited, however, to one of the three numbered suits. With suji, the waiting pattern involves one of the three mahjong intervals.
Ryantan (a contraction of ryanmen + tanki) is composed of a triplet of a middle numbered tile with one more tile adjacent to the number, either one less or one more. The single tile produces a tanki wait when we keep the triplet complete, and produces a ryanmen wait when we split the triplet into a pair and connected tile.
Sanmentan (a contraction of three-sided tanki) consists of three tanki waits along suji lines. This pattern is created through seven consecutive tiles.
A number of three sided waits remain unnamed. Instead, they are composed of named waits as combinations of each other.
- Sanmenchan in Japanese Wikipedia