I need to give a usergroup permissions to close threads

[superb]

Thanks again for your input.

The idea is to have a menu option on the thread tools menu that only allows them to close the threads automatically adding a [closed] prefix to the thread once they use it.

All users of this usergroup would be able to close threads but only using this option that will automatically add a prefix to the thread when closing. They will not be able to edit titles and not be able to re-open the thread once it is closed either. That's the idea.