Walkie Talkie Seven
In this shape the point is the vital point. A Black play there (or at any of the other internal points except the point a) leads to 6 points of Black territory.
If black has two or fewer outside liberties, which is likely given the shape, then White can turn this shape into a throw-in ko or a seki. With more outside liberties, White cannot achieve anything.
Two or fewer outside liberties
If white takes the vital point with . Black's best response is at
(but see later what happens if black plays
). After
, Black can only play at a to make a ten thousand year ko.
(Black at ''b' results in death in gote because White doesn't even need to answer black; the shape is dead as it stands.)
Ten thousand year ko
If Black connects at a, his eyeshape is reduced to a pyramid four, and therefore Black is dead. Playing on either of the points b allows White to capture at a and this puts Black in atari. Unless Black is komaster with big ko threats, he is unlikely to want to play on either point b.
Letting White capture at a and connect at turns this a position into a seki.
Playing out the ko
If Black plays elsewhere instead of starting the ten-thousand year ko, White can try to capture the corner by playing out the ko. However, White will need two more ko threats than Black, and Black will get to play four moves elsewhere in exchange for the corner (,
,
, and
). If White doesn't have enough ko threats, an option is to back down by playing
at
in the first diagram to make a seki, but Black would still get to play three moves elsewhere (
,
, plus one more move elsewhere after White makes seki).
Hence, it would be difficult for White to win the ko without being komaster.
Therefore if white has not enough ko threats it is best to leave the position after in the previous diagram.
( and
= tenuki;
takes ko at
)
Thus, when neither side has enough ko threats, White can also settle for seki. This is a little better than playing the ko above and then making it a seki.
But because all black can do is get a seki is not urgent and above that removes the earlier posibilities for a ko (aji keshi).
It should and therefore only be played at the end of the game.
variation for
This way the position becomes a direct ko, which is an inferior result for Black. White can finish the ko by filling at - it would be a mistake to play one of the other inside liberties instead.
Three or more outside liberties
Although the situation shown here is perhaps unlikely to occur in real games, it is of theoretical importance. If Black's group has three or more external liberties, White cannot achieve anything yet, as Black can set up an oshitsubushi as shown.
(Note: can be used as a large ko threat if the Black group has exactly 3 external liberties.)