To find out what stairs you can currently challenge someone in, first go to the Main Stairs Page, then click on "Show your stairs only" link. The ones in BOLD are ones you can make a challenge in. .
estanto: Well that is one thing I like about BrainKing's stairs - they did not just copy another system, but tried to do a few things different to try to make it different for the site.
I'm sure if problems arise where players are unable to challenge people, and such and something like being able to challenge above would fix it, Fencer would look into doing that. But right now, the system is working great how it is. My opinion is to try it how the system is now, and once (if) something does not work, then would be the time to start thinking about being able to challenge above yourself - but since when someone loses, I believe there will always be people at the bottome and near enough to you to always be able to challenge people at the same (or below) your level to earn your way up to play the top players. (instead of skipping the same level people and jumping up to challenge the top players right away.)