Download this mod
This mod adds the feature of marking a topic solved or unsolved. You can select the boards this feature to be active. It includes solve own topic and any topic permissions. It also has quick moderation option when selectboxes are used and topic solved log, which can be viewed both from Admin Logs are and Moderation Center.
To enable the mod:
Admin Control Panel >> Boards
Click on the "modify" link for the board you want to enable this feature for.
In the edit board page check "Topic Solved Board" option and save the changes.
Note: This mod uses FamFamFam Silk icons licensed under Creative Commons Attribution 2.5 License.