There is a well-known pattern, occurring often in handicap games, which starts with a kosumi tsuke.
There are several things worth noting:
Let's have a closer look at the implications, with diagrams
Here, the marked handicap stone in the previous diagram is absent. In this case cannot in general gain an advantage: White becomes strengthened and the black corner isn't secure territory. (Charles). See also section (ii) of Joseki as a source of bad habits. (phenomene)
The follow-up at a is not at all compulsory, either in amateur handicap or in even pro games. White will often tenuki and leave her options open, including b to d. A pincer to the right of the marked stone can also be expected.
What happens if Black doesn't even grant White her shortest extension?
From pro play, where is mostly absent, we see that this sequence can be called a set pattern.
is a good empty triangle, denying White good shape.
covers his cutting point and
does likewise.
If here instead of
in the previous diagram, White can cut and squeeze. Black 11 at a and Wite will protect her cutting point at b or c. This takes the fire out of the attack.
This is also seen, but there is a ladder issue. White denies the good empty triangle but ends up with a mediocre shape anyway.
DaveSigaty: Generally bad, hmmm... Rare I will grant you. But from time to time the duffers dust off this old chestnut! :-)
Go Seigen - Hashimoto Utaro (Black) Ten Game Match in 1947
Awaji Shuzo - Cho Chikun (Black) 3rd Kisei Preliminaries 1978-07-06
Yi Ch'ang-ho - Yoda Norimoto (Black) 10th TV Asia Championship 1998-08-12
Yu Ch'ang-hyeok - Ma Xiaochun (Black) 1st Toyota & Denso Cup 2002-03-19
Shao Zhenzhong (B) against Cao Dayuan, Chinese team tournament, March 28, 1990.
It seems that professionals do in rare cases play this (pseudo-)joseki, typically when the player playing it is strong on the side. The idea is undoubtedly that a short extension (to a) is overconcentrated, but a longer extension like here leaves black open to an invasion and thus an attack. Prerequisite is that black is strong enough that this invasion must be considered important aji. - Andre Engels
Authors
March 2003: rewritten and rereferenced, rather than WME. A.o. material now to be found at BQM82. Dieter
[1] Bill: I'm surprised that the full pattern occurs that often in pro play. In a handicap game, how often will White play ? Even if it is technically correct (honte), it seems too passive for a handicap game. In an even game, I would think that Black would have to be quite strong in the surrounding area for
to be right.
Charles When Black attacks with the most common reply is
here. This gets White out into the centre and builds some influence. I can imagine White playing at a instead, for immediate life: that play is good for eye shape. But if White tries to live locally, Black at b becomes very good, to secure the corner while attacking. Therefore early in the game I'd expect
or something in that direction.
What about cutting immediately after the attachment? Guo Juan showed me this variation.
Charles Well, if she showed you, maybe you can show us? If is played immediately, without a favourable ladder, it might be an overplay.
goantti A bit similar position occurs in the 1st Japan's Strongest Deciding Matches. Sakata Eio plays the cut against Go Seigen. Naturally white has the ladder.
The white move 10 should be at A for good shape, but then black gets B.
White lives in the corner, and next black plays around a to live on the side. In the game it was possible to exchange b for c before a.
In the Guo Juan -diagram a more severe pincer was possible, so the cut might work better than for Sakata (he eventually lost the game).
This position has occurred in some pro games. The most common idea is this , to make some shape.
Well, one can guess that is played in cases where the contact play at the marked point would turn out to be an overplay.