Don't overreach!

All the framework links are secure so it is time to apply the ninth directive. The framework square A-B-C-D has created the biggest territory and it is Black's turn to play. Which is best from the points E, F and G?

E is not very efficient. It solidifies the D-C link but leaves the side territory under C undefended.

F both protects the side territory and strengthens the link and is the recommended move. It is easily connected and is therefore very safe.

But why not one intersection further at
G?

The overreach

Black might wrongly anticipate a meek reply at H but after black 1, white 2 is set on a counterattack via a threat to cut off the black stone. At this juncture Black could reconsider, but black 3 is the only move fully consistent with black 1. But with white 4, White aims at making some inroad into the large black territory.

Black 5 resists. After white 6, black 7 aims at fencing off. But to Black's horror White has the counter-intuitive white 8. Black 9 takes one stone. White 10 is atari upon black 9. The best that Black can manage is the atari black 11. See next diagram.

The inroad

White 12 captures one stone. Black 13 (atari) seems to block White's route. White 14 captures one more stone. Now Black could recapture a stone below black 13 but this would be ko and White has the better ko threats. So to cut a long story short - eventually a stone at black 15 must be played to protect the most vulnerable atari cutting point. But even so white 16 is double atari and forces black 17. White 18 captures one stone forcing black 19. And still White is not finished! By sacrificing white 20, the sequence to white 26 denies Black the edge territory that black 1 was originally aimed at.

This particular sequence represents a significant loss of territory for Black, but the player does not have to calculate every possible sequence before deciding where to play, but instead develop an intuitive judgement based on the framework gaps and potential aji of isolated stones.