Mark Solved Button

I wasn't seeing the option for this, but a Mark as Solved button would be good so we know when a topic has been resolved.

Example:
PHP Freaks

Poking around the phpBB Mods database I didn't see anything, but maybe someone knows of a publicly available one.

Admins/Moderators/Helpers could also be given the power to mark other threads as Solved to help keep things cleaned up.