Add a "Mark as solved" link at the post starting a thread.
To help people to mark their questions as solved a link "mark as solved" or "solved" would be helpful.
Good place would be the line of the existing links at the right of first post in a thread, visible to the thread creator and maybe to the moderators.
quote link report solved
It is interesting idea.
I think it would be useful.
+1 or maybe a nice button beside the title
It would be very helpful.