Placement preventing the tower peep

Good before tower peep  

is Black's countermeasure to White's tower peep at a. The outcome here is a beautiful mouth shape for Black.

Good after tower peep  

Even after White makes the tower peep at and attacks strongly, is still available to make shape.

(sigs) maybe some info about what happens if white ignores the tesuji and does the tower peep anyway?

JanDeWit writes: No comments at all given, but I'll write my own thoughts here.

In the upper diagram, is dead, but the rest of his stones are bearing down strongly on White. White can't cut towards the center (at a for instance) because then she's placing herself in a pre-made geta.

The other diagram shows what happens when Black plays tenuki (to account for the change in color of , right?). Now has made inroads to the center and is danger. On the other hand, Black seems to have made some territory at the top; but White's stones are still connected, so it doesn't look like Black can get much further there. All in all, White has pushed in a lot when compared to the first diagram.

This isn't exactly a beginners' tesuji, in my humble opinion...

HolIgor: No, they are not beginners' tesuji. They are for advanced players. They should be played in the case when the black stones in this part of the board begin to feel lonely and threatened. Each of these tesuji gives Black at least one eye and builds a good shape, which is difficult to attack. As the black stones in this part of the board are in the minority, Black should not think in terms of building territory here. Just surviving is OK, surviving without strengthening your opponent too much is ideal. The territorial interests are somewhere else. Getting good shape for the stones helps to live, and as soon as your stones live they may be used to build an attack.

I didn't even notice the double atari at b!

HolIgor: It is supposed here that the double atari arising does not matter much - that the two black stones may be treated lightly, that they are not very important stones.

AYHAL: the pros say that the tower shape does not occur in pro games often, they consider it to be defective.

Velobici: This is discussed in Sakata's book Tesuji and Anti-Suji of Go. Used that information to discomfort an AGA 1k not too long ago. He started playing more determinedly after that.