Ladder mount for Overhead Bunk

I just now decided to make up the queen bed in the overhead, but when I went to hook up the ladder it was too short. It looks like there is supposed to be something mounted to the edge of the bed because there are two what look like clamps spaced to the width of the ladder and they are held in place with two screws each.
Can anyone tell me what might be missing or how to get the ladder mounted. I can put a platform down on the floor and just angle the ladder to the bed but I think there is something else that goes into these two clamps that hangs down.
Anyway, any help would be appreciated.
Thanks,
Jake