Study recommended for 10 kyu or stronger.(Show more of this level)
in the corner is a move that requires a lot of reading.
If black does not play this move, then white has the ability to create a ko in the corner.
Keep in mind though, that the ko is not always in the advantage of white. In that case black does not have to play this defensive move.
The following sequence has been seen in a game of Dai Jiashen (7p) and Yang Mengyun (1p), played in november 2004.