The tsuke-nobi (or attach-and-extend) joseki is formed by the moves to in this diagram.
Its name comes from Black's plays in this diagram: is a tsuke (attachment), and
a nobi (stretch).[1]
The tsuke-nobi itself is mostly popular among weaker players, but for stronger players it is still a good idea if Black wants to build thickness towards the left side, and does not mind giving White a position on the upper side. In other words, Black regards the left side as more important than the top. Often, but certainly not always, there will be a black stone around the marked point. After , White at b, d, e and f are all joseki.
In pro games it is now rare unless justified by the context: either Black getting a very efficient formation relative to the left side, or White getting an overconcentrated formation at the top.
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Tenuki next for White isn't a good idea at all. If, for whatever reason, White allows Black to play the next move here, Black should not hesitate to play b. The resulting shape is very good.
[1] See also other possible joseki choices after .