rail stiffners(long pieces of aluminium) under the caps, you have to give the caps a pretty good jerk to get them off, i only pulled them off about half way to put the stiffners in, no big deal but try to be careful as you can so you dont break all of the ears off the caps so you can reinstall them, i only broke one off of mine. Just read the instructions first and the rest is pretty basic.
CW