I assume you're asking so you can perform the required 'bump' for your post on the DVC Rent/Trade board.
Read the posting rules at the top of that board. They explain how to 'bump' a thread so the automatic software that analyzes all threads on that board will recognize your 'bump' and not automatically lock your thread.
Basically it's simply making a reply to your own thread with the single word bump as the text of the reply.