With phpBB 3.1, you will need a extension. If you don’t find one that fits your needs you can always go to the ‘Extension Request’ forum and request one
Just get in to the habit of locking the topic with a reply. There's a lock option below the reply box so the person doing it can just post saying 'locked' and do the whole thing in one action.
-:|:- Support Request Template -:|:- "Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb"