On Runescape.com official forums (or at least how they had it, 2 years ago when I last played), on your own thread, or another thread, you can see the word "Bump" in the top. You click it, and it doesn't add a post to the thread (to reduce spamming), but it bumps it to the top of the list. A thread owner can bump his/her own thread once or twice, and then the option disappears and it's not allowed anymore.
08-01-2009, 05:18 PM
"Bump" Feature
Threaded Mode