Tapir / Woodwork

Sub-page of Tapir

I need a project... exploring carpenter's squares may well help my reading ability.

Table of contents Table of diagrams
The carpenter's square
The carpenter's square
Ko N°1
Ko N°2
A refutation (why B4 can't be at W5) - killing by nakade, the number of black's outside liberties doesn't matter
White achieves less (though still ko) not more
White achieves less (seki) not more
Ko N°3
With B4 capturing another ko emerges - but it is better for White than the usual one
B4 connecting doesn't work at all
A refutation (black deviates with B4) - here outside liberties are important
Black can't block with B8
Try for Ko N°4 (s. with one liberty) - this B4 doesn't work
Better try for Ko - this B4 does work
After W3 Black is dead ([LeatherScrollProblem144/Solution])
Black is dead I
Black is dead II
Black is dead III
Failing moves
Failing move ''d'' - not even seki
Carpenter's square with one outside liberty
Ko N°1 fails - after white takes the throw-in, black can approach at ''a'' and kill white
Ko N°2 works
A refutation (why B4 can't be at W5)
Ko N°3 - main line
Ko N°3 - variation (only playable with outside liberties)
Refutation of deviation (B4 at B6) in the variation (B6 at W1 to avoid ko)
Ko N°4 - White can resolve the ko at both ''a'' and ''b'' (if black connects at ''a'')

Ko N°2
Index of sub-pages


Carpenter's square

The carpenter's square is unsettled. B1 is the vital point, making it unconditionally alive.

[Diagram]

The carpenter's square


No outside liberty

[Diagram]

The carpenter's square


First move 2-2 point (a)

[Diagram]

Ko N°1

W9 at B10 and B10 at W9 is seki.

If white loses the ko, black has 7 points (3 net captured stones, 4 territory) in the corner + a later one point sente reduction on the first line. (Note: all first line follow up values given here and later depend on the exact configuration of stones on the outside.)

This is the best play by white.

[Diagram]

Ko N°2

If Black wins the ko, he will resolve it by capturing W3 and W5, black ends with 9 points (3 net captured stones, 6 territory), Black can later reduce white left edge territory in sente by 4 points for a difference (and has reduced one point already) of 6 points to ko n°1. Thus this ko is worse for white.

[Diagram]

A refutation (why B4 can't be at W5) - killing by nakade, the number of black's outside liberties doesn't matter


White 7 deviates (ko n°1)

[Diagram]

White achieves less (though still ko) not more

If Black wins the ko it has a 4 point sente endgame on the upper side (and has reduced one point already) and a bigger corner (5 net captured stones + 5 territory) than in original ko n°1. The difference is 8 points (16:8)

[Diagram]

White achieves less (seki) not more

White needs two moves to almost fill the corner and in this process she can't make a dead 6-point-shape inside so this ends in seki. This seki usually is even worse for white than the above ko. (If white wants a seki, she can make a better one by deviating with W9 from the normal ko n°1 line.)


First move hane (b)

[Diagram]

Ko N°3

If Black wins the ko, he'll resolve it by capturing W7 and W9. Black has 10 points in the corner (5 net captured stones + 5 territory), he can further reduce white along both sides in sente by 5 points. The difference to a lost ko n°1 is 12 points.


Black 2 deviates

[Diagram]

With B4 capturing another ko emerges - but it is better for White than the usual one

White can't answer B8 with a because this ends in double ko life for Black. But if White hasn't enough threats left, she can still settle for a - with the double ko life giving an infinite amount of ko threats for White / later two moves in a row if Black is finally going to resolve it. Thus this is a lot better for White. (I'm not sure about the ko with B8 at b)

[Diagram]

B4 connecting doesn't work at all

B4 connecting is wrong, White wins the eye-vs-non-eye semeai B6 at B8 (changing move order) do not change the result.


Black 4 deviates

[Diagram]

A refutation (black deviates with B4) - here outside liberties are important

Black can't approach at a and dies.


Black 8 deviates

[Diagram]

Black can't block with B8

Here white kills by nakade, so outside liberties don't matter.


First move clamp (c)

[Diagram]

Try for Ko N°4 (s. with one liberty) - this B4 doesn't work

[Diagram]

Better try for Ko - this B4 does work

If Black wins the ko, this should be as big as ko n°2 (9 points in the corner + 5 point sente reduction of white upper side territory).


Black 2 deviates

[Diagram]

After W3 Black is dead (LeatherScrollProblem144/Solution)

If W3 connects out, black is dead, if white can fill with dead shape + eye (so that it can not be seki) it is dead. So actually there is no way to live.

[Diagram]

Black is dead I

White built a dead shape inside with an eye in the corner.

[Diagram]

Black is dead II

This is no dead shape, but white wins the eye vs. non-eye semeai with 3 vs. 2 effective liberties. This line is sensitive to outside liberties and doesn't work with black outside liberties.

[Diagram]

Black is dead III


First moves that fail

[Diagram]

Failing moves

While f and g are obvious failures - e.g. after a black answer at the vital 2-2 point - d and e merit some discussion. CarpentersSquareWrongAttack discusses e (against which Black stretches for at least seki) in detail.

[Diagram]

Failing move d - not even seki

This is pretty similar to a first move at e - with the additional (and bad) exchange of W1 for B2, which disables the seki lines.

One outside liberty

[Diagram]

Carpenter's square with one outside liberty


First move a - 2-2 point

[Diagram]

Ko N°1 fails - after white takes the throw-in, black can approach at a and kill white

[Diagram]

Ko N°2 works

[Diagram]

A refutation (why B4 can't be at W5)


First move b - hane

The refutation of B2 at B4 see above, doesn't work with outside liberties, the refutation of B4 at W5 as well... so everything changes. (below diagrams to be changed).

[Diagram]

Ko N°3 - main line

[Diagram]

Ko N°3 - variation (only playable with outside liberties)

[Diagram]

Refutation of deviation (B4 at B6) in the variation (B6 at W1 to avoid ko)

Black can't avoid ko, if he tries with this B4, he dies by nakade. If not, he has just another ko. But this ko may be worse for white in the endgame if she loses the ko since B4 is in place already.

First move c - clamp

[Diagram]

Ko N°4 - White can resolve the ko at both a and b (if black connects at a)


Two outside liberties

[Diagram]


First move at a - 2-2 point

While ko-variant N°1 fails as with one liberty, the N°2 ko works as usual.

[Diagram]

Ko N°2


First move at b - hane


First move at c - clamp


This is a copy of the living page "Tapir / Woodwork" at Sensei's Library.
(OC) 2011 the Authors, published under the OpenContent License V1.0.
[Welcome to Sensei's Library!]
StartingPoints
ReferenceSection
About