British Go Journal No. 14.  June 1971. Page 11.
Katachi is Japanese for shape. An expression such as 'this is katachi' means the shape is good and effective. Good Go depends critically on understanding and use of katachi at all stages of the game.
Why is katachi so important? To achieve formations economically it is necessary to use every stone to its full, and so we must learn the key points in common shapes that occur in every game. An ability to recognise these key points quickly and certainly cannot fail to raise your strength.
One aspect of good katachi is that with such formations eye-making becomes much easier - the stones work together efficiently to make eyes and thus are resilient when attacked. Let us look at this in terms of very simple diagrams and work from them to less obvious positions.
Diagram 1 ||
Diagram 2 ||
Diagram 3 |
Dia 1. This position (known as ponnuki) is very efficient and strong, as the minimum number of stones has been used to make an eye.
Dia 2. After white 3, black 4 is a good move as it prevents white achieving the strong position of Dia 1. Now white's position is much weakened by the presence of black 4.
Dia 3. Moving one stage further back, black
1* occupies a vital point in this position, as
would moves at A, B or C.
* [ BGJ had black 3. ]
Diagram 4 ||
Diagram 5 |
Dia 4. What about this very common position? A little consideration shows that white 2 is a vital point, and so black 1 is almost unconditionally forcing - just as he intended.
Dia 5. White can never let black play at 1 in this position. You should see the analogy between this position and the proverb "Play hane at the head of two stones".
Diagram 6 ||
Diagram 7 |
Dia 6. This position comes from a well-known joseki. Black 2 is one of the vital points - and a joseki continuation, although rather complicated.
Dia 7. In this case, however, black 1 is much too slow. White has already played one of the key points of the formation, so Black, if he wants to play for the outside, should play at A or B. Black's move is good when White's stone is at C.
Diagram 8 ||
Diagram 9 |
Dia 8. White is severely attacked in this diagram by black 1, the 'eye-stealing' tesuji, and worse, he must give black sente for further attacks when he connects at 2. White should have played ' at 1 first.
Dia 9. White 1 is katachi, as it gives him the chance to play at A or at B and either way to make a second eye. These points are now miai , that is , white is certain to be able to play in one or the other of them and so secure life.
Try to apply these ideas in your next game - these shapes will almost certainly appear in it.