4-4, double low approach, attach-extend, 3-3 invasion
When enters the 3-3 point, and is a common joseki for controlling the upper side.
If Black has support at or a, then will be played here instead of b to avoid overconcentration.
may also choose to connect, in which and are sort of a tesuji. After , if White a then Black b, and if White b then Black a, so Black may have an opportunity to attack the White stones at the top.
If is played at , then Black c takes the corner.
The hane at here is rare in professional games, because and connects the corner to the top side, acquiring a sizable amount of territory and possible expansion along the top side. In compensation, Black gets a wall on the left side, but it appears inferior to White's territory.
This sequence is seen in a game between Huang Dexun (White) and Jiang Zhujiu (Black), colours reversed. The game took place in China, 1981, with Black winning by resignation.