Removing a Dell EqualLogic 4000XV from the rails?

I am trying to remove a Dell EqualLogic 4000XV from the Dell rails. How do I get this beast out? I removed the drives and power supplies. I unscrewed the thumb screws on the front. I also removed the screw on the back. I can not see what is holding this thing in. I can only get to one side but do not see anything to release. What is the secret?

Thanks.