There is Death in the Hane

Example 1  

The hane at kills the Black group by reducing the eye space to a bulky five dead shape. If Black tries to capture at a, this does not gain an eye.

Example 2

Example 2  

This Black group (an L+1-group) can be killed with the hanes at and . If Black blocks at a, Black's interior space is a dead bulky five. White can then kill Black with a placement tesuji at b. If Black tries playing b instead, then white will play a.

Notice that in the above examples, the hane stone is not defended when put into atari. Instead another hane or a placement follows. That is because capturing the hane stone will result in a false eye, and White can easily prevent Black from escaping to the outside (see preventing escape on the first line).