In the game of
Go (
Wei Qi/
Badouk) a "wedge" is a play between two formations of the opponent's, usually in the middle of an open side of the
goban (board) when the opponent controls both adjoining corners. It is usually played on the
third line in the middle of an open area at least 9
rows (or
columns) long, allowing a
niken tobi (
two-space jump) move into open space on either side to build a
base. The purpose of this move essentially to prevent the opponent from playing at that point himself, thereby laying a fairly strong claim to that entire side of the
goban.
A typical example of a wedge is shown here (whole bottom side of the goban shown, edge marked with ###:
#...o...........x...#
#.oox.....,.....,...#
#ooxx....b..o..a.x..#
#xx.................#
#...................#
#####################
("," are hoshi (star points) and can be ignored if you don't know what they are, since they are for reference only and have no game effect)
White is "o", Black is "x." White has just played the wedge stone (the o in the middle) between Black's strong corners, in order to prevent Black from dominating that entire side. If Black now approaches at or around the point marked "a," White will usually respond at "b," to build a base. Conversely, if Black approaches at or around "b," White will play at "a," for the same reason. Note that this means that "a" and "b" are miai (equivalent points). This is the main idea of a typical wedge; to play in the middle of two formations of the opponent's stones, such that it is possible to build a base, regardless of the direction the attack comes from. Once a group has a base on the third line, it is usually safe to assume that it can live, assuming there is at least a little bit of empty space around it to make eyes, and assuming the player takes appropriate measures in face of a continued attack.