White might try to play hane at in order to play in sente. If black gives the usual answer, a and b are miai for life. If is answered with white would have a chance to escape at .The correct answer is to keep following on the second line with or throw-in at to reduce eyespace.
One of the simplest refutation to the hane of is . After and , it is not possible for Black to play at a.
The squeeze of allows White to play atari in the direction of .