I found that the whole trap is a bite bar. I don't use them and most if not, all rats will have thier teeth hooked in the top section of the trap.
I agree almost all rats will be in the corner or top locked in. I did see where a colony trap door was an inch or two under the edge where you would normally put the top of the door. They added a section of 1x2 or 1x1 across the front along the top, then put the door on to the bottom of the section across the top . This way the rats would be up in the corner or above the door and the door could still swing freely. I know I saw a pic on it here somewhere. Hopefully someone can put it in