Ear-cleaning tesuji  

is the ear-cleaning tesuji, forcing Black to protect with a, b, c, or d.

In Japanese, mimi-souji.

Examples from professional games

Here's a real-life example of the tesuji taken from the 2005 Meijin league:

Kobayashi Satoru (B) vs. Cho Sonjin (W)  

is tesuji, Black uses it to help his weak group make shape while attacking White. Black goes on to win this game by resignation.

could have resisted at a

Lee Sedol (B) vs. Tang Weixing (W)  

White played but a was also an option.

Treatment

Angle point  

1. If you look at , and , you see that sits on the 'angle'; even if Black plays the circled point, no eye here.
2. This shape would therefore be better for Black with at a, weakening .
3. This shape would be even better with at a.
4. In that case, we probably do have White b, Black c in the near future for a bamboo joint; but this is strong for Black, who can then move out easily in several directions.

Context is, as usual, important. Assume first White is attacking here. Then White's attempts to cut are irrelevant (won't happen any time soon) - but Black presumably must connect somehow. In that case the connection with is shapeless.

If on the other hand White is on the defensive you perhaps look longer at White's forcing plays. But then wouldn't be played this way, in most cases. White normally gets more by playing at .