Just like bumbershoot said, can only move backwards. And Disney is really serious about it! All corrals are gated off and each persons bib is checked upon entering their corral. You may hear stories of someone moving forward but it's very very rare and I still don't know how they manage it. I had to enter and exit the corral a few times (nervous nelly bladder, ha ha) and there were always people trying to get in, and I was pretty far back (didn't submit a time and neither did my friend). She was in two corrals ahead of me but moved back to run with me! Good luck and enjoy the race!! It's going to be amazing!