In the game of Go (Wei Qi/Badouk), despite the large size of the board (called a goban in Japanese), there are essentially only five commonly played opening moves (six, if you count tengen, but that's rare). The board is symmetric and initially empty, so there are actually 24 such points, eight in each corner (one san-san, one hoshi, and two each of komoku, takamoku and mokuzuhashi), but from the point of view of the first move, all corners are equivalent and the pairs of off-diagonal plays in a given corner are equivalent as well. The standard etiquette for Black on his first move is to play in the far right corner, from his point of view. If playing an off-diagonal move, it should be on the right side of the diagonal. In the diagram below, the Black stone (X) marks san-san, the opening move we will discuss here, while the points marked "o" are other more-or-less common first moves.

```   a b c d e f g h j k l m n o p q r s t
19 . . . . . . . . . . . . . . . . . . . 19
18 . . . . . . . . . . . . . . . . . . . 18
17 . . . . . . . . . . . . . . . . X . . 17
16 . . . + . . . . . + . . . . . o o . . 16
15 . . . . . . . . . . . . . . . o o . . 15
14 . . . . . . . . . . . . . . . . . . . 14
13 . . . . . . . . . . . . . . . . . . . 13
12 . . . . . . . . . . . . . . . . . . . 12
11 . . . . . . . . . . . . . . . . . . . 11
10 . . . + . . . . . + . . . . . + . . . 10
09 . . . . . . . . . . . . . . . . . . . 09
08 . . . . . . . . . . . . . . . . . . . 08
07 . . . . . . . . . . . . . . . . . . . 07
06 . . . . . . . . . . . . . . . . . . . 06
05 . . . . . . . . . . . . . . . . . . . 05
04 . . . + . . . . . + . . . . . + . . . 04
03 . . . . . . . . . . . . . . . . . . . 03
02 . . . . . . . . . . . . . . . . . . . 02
01 . . . . . . . . . . . . . . . . . . . 01
a b c d e f g h j k l m n o p q r s t
```

The name of the point shown above, san-san comes from "san," Japanese for "three." It should be clear, then, than san-san is the 3-3 point - that is, three steps in from the corner of the board in each direction. R3, C3 and C17 are also san-san points.

Of the feasible opening moves, san-san is the most territorial. By playing this point, a player essentially guarantees himself territory in that corner. The downside is that san-san does not offer much opportunity for positive development along the adjacent sides of the board, and allows the opponent to build a good deal of influence towards the center of the goban. It is a far less popular choice of opening move than either hoshi or komoku, but is well-liked by some professionals (such as Cho Chikun) when playing White. Although shown as a Black move here, it is rarely played by professionals as Black because it makes it hard to overcome White's komi (points added to White's score to compensate for Black's first move advantage).

One of the features of san-san is that it is very stable, so it is neither urgent for the person whose stone it is to extend from it, nor for the opponent to play a kakari (approach move). Eventually, however, such a move will be played.

If the person who played the stone is going to play again in this corner, it will generally be an ogeima (large knight's move) extension, at one of the two points marked with an asterisk (I'm now only showing a quarter of the board, since we're only concerned with the local position).

```k l m n o p q r s t
. . . . . . . . . . 19
. . . . . . . . . . 18
. . . . . . . X . . 17
+ . . . * . + . . . 16
. . . . . . . . . . 15
. . . . . . * . . . 14
. . . . . . . . . . 13
. . . . . . . . . . 12
. . . . . . . . . . 11
+ . . . . . + . . . 10
```

Such a move increases the influence of the corner and gets up off of the third line, but doesn't establish much more territory along the edge, because it still leaves Black with an open skirt until a further stone is added on that side.

If the opponent ends up doing something about the san-san stone before such an extension is made, a direct shoulder hit is the most common way of going about it, although playing at one of the asterisk-marked points above is also seen, going by the philosophy that "the opponent's good point is your good point." Assuming the shoulder hit at the 4-4 (hoshi) point is played, the most common joseki is the one shown below (White at 1, Black at 2, White at 3, etc.)

```k l m n o p q r s t
. . . . . . . . . . 19
. . . . . 4 . . . . 18
. . . . . . . X . . 17
+ . . 5 . . 1 2 . . 16
. . . . . . 3 . . . 15
. . . . . . . . 6 . 14
. . . . . . . . . . 13
. . . . . . 7 . . . 12
. . . . . . . . . . 11
+ . . . . . + . . . 10
```

After the shoulder hit, both sides pushing once at 2 and 3 is inevitable (note, though, that the Black san-san stone and White's shoulder hit form a symmetric position, so the mirror image joseki could also be played, depending on the whole board position). Then Black 4 and 6 serve to establish secure life and at the very least 12 points of secure territory in the corner for Black. Meanwhile, White 5 and 7 confine Black to a fairly small region in the corner, establishing some power facing the center in the process.

Given the result of the above joseki, and other variations (most of which turn out with a similar result, although some give Black more development potential while focussing White's influence down one side of the board), the choice of san-san as an opening move should be made by a player who likes to take territory early on and is comfortable with having to deal the opponent's influence in the middle game. Because it also has somewhat of a simplifying effect on the game, it is worth considering for Black in a no-komi game, or White in a game with komi. As mentioned above, it is generally not seen played by Black in an even (5.5 or 6.5 komi) game by strong players.