3-4 point low approach two-space high pincer one-point jump
This play for White in the 3-4 point low approach two-space high pincer was hardly tried before the 1960s. White looks to settle himself; but there are variations involving a difficult fight.
The main ideas now are Black at a, permitting White a slide on the top side, or b denying it. Also played are Black c and d.
If Black 1 here, White in pro games has tried a counter-attack on the left (one of the points a), or at b to take a key point of shape. It seems there is no definitive joseki yet.
If Black omits ...
tderz: If Black omits above ...
then could become the biggest move despite being on the 2nd line. It is big because it is flipping the defensive/offensive properties (I would like to formulate this better) of the group. Often it could be considered an urgent move (I think there is an example in Yang Yilun's Fundamental Principles of Go).
becomes a little bit meaningless.
Bill: IMO, after you can consider as a kikashi stone, inducing the low instead of a normal extension.
tderz: Good idea indeed! White is quite low and black got an additional move. It must be the specific position, which makes the difference between above and here bigger.
Bill: Well, I'm not up with the latest on this joseki, but my references do not show in any variation. <shrug>
from the side is a major alternative. White wants to stop black from extending along the left. Usually white will have a position in the lower left to back this move up.
Black keeps the white stones separated with and , after which there is a turning point.
White can go to the corner with . Black can play at a, keeping white out of the corner but allowing him to strengthen himself, but black can also build thickness with the combination of and in this diagram.
This same joseki with at a has also been experimented with.
If white pushes in the center with , black can still develop the top with to . After this, white is unlikely to attach at a right away, because the cut in the previous diagram is now too painful.
Nevertheless, black will often secure the corner fully with and , allowing white to claim the top with .
One move amateurs are prone to play which is actually bad, is pushing with here. Even though white might be building up thickness for an attack on , pushing black along the fourth line like this gives up too much.
Charles Matthews, Andre Engels