# Two-Space Notchers

Keywords: Life & Death

Two-space notchers are groups that consist of a chain on the second line, interrupted by a notch of two empty spaces on the second line and two to four stones on the third. The term was invented by James Davies. See also Notchers, One-Space Notchers and Three-Space Notchers.

Two-space notcher

The rule for two space notchers is, depending on how you want to formulate it, either "Five die, Seven live" or "Six is unsettled". For the time being we'll leave proof of the two extremes to you and demonstrate the unsettled case.

Black goes first and lives

If Black goes first, he can live. White is again rather stubborn to keep trying with 2 and 4, but after 5 Black has completely constructed the two eyes he needs to live.

Eggplant86: isn't it better style for B to move black 1 to black 3? I don't see a way for W to kill and it could be better yose.

White goes first and kills

White can start his attack with a hane at 1.

(Reducing your opponent's eye space like this should always be the very first option you consider when examining the status of one of his groups, by the way. See also the article on How to approach a life and death problem.).

Even if Black were to resist, White can keep his group dead.

### Classification

Two-space notchers

Marked spots: possible weaknesses
Marked stones: legs

211WW
211WN
211WS
211NN
211NS
211SS

212WW
212WN
212WS
212NW
212NN
212NS
212SW
212SN
212SS

### 222

222WW

aka the flying saucer shape. It is dead

222WN

Black can live

222WS

Black can live

222NN

Black can live

222NS

Black can live

222SS

Black can live

tapir: Black can tenuki twice here. Actually, for white has to surround first before trying to kill.

213WW

213NW

Black can live

(...)

223WW

Black can live

223WN

Black is alive

(...)

### All 223 are alive, except for 223WW, where Black can live and White can kill.

However, 223WSNotcher shows a killing sequence for White.

233WW

Black is alive

(...)

### Table

Two-Space Notchers last edited by 24.205.32.92 on January 1, 2013 - 18:05