How do you open the guard door mouth on riddle transfer?

Get all the prisoners in their cells out excluding Diz because he's inside the guard door. After you get all the prisoners down to B2 go to the guard door and click on it. Then he should open his mouth. Next go to the power room (B1) and click on the screen that turns the guard door on and off and look at it. Wait until the guard door closes his mouth and then turn it off. Then the entrance should be open. Go inside and get Diz out. Sorry I couldn't tell you how to get the prisoners out or what to do once inside Diz's cell.