You may either top the topic Permanently, in which case it will be marked as a topped thread and remain at the top of the forum listing until it is de-topped. Or you may top it Temporarily, in which case it will act as if someone just replied to it and be bumped to the top of the forum listing only until the next post is made (note: the date on the thread will not change).

   Temporarily (until next post) top topic.