Lens Hood Question

This has been puzzling me for a while - The hood that comes with the 18-55 kit lens has a small section on the underside that can be removed. It is clearly marked 'OPEN,' with an arrow, but I can't think of when one would want to remove it. Any ideas?

polariser filter

To expand upon that, removing the cover means that the polariser can be rotated without having to remove the lens hood.

And that's one of the things that makes Pentax unique. They think of things like that. They did it on the 67, too.