Maximise the territory!

White 1 threatens Black' framework. How should Black respond?

Safe!

From a previous example you may recall that black 2 makes certain of connecting both framework links. But white 3 and 5 depress the black boundary. Can you see how to do slightly better?

Maximum!

After black 2 both framework links can be connected but this time the boundary is better. A white stone played at A would be answered by a black stone at C necessitating a further white stone at B, thus losing the initiative. So instead it is correct to imagine a white stone at B answered by a black stone at A. This would clearly be two points better for Black and two points worse for White i.e. a swing of four points to Black compared with the previous diagram.