I am often on guineapigcages.com looking at their cages, and they have cages made for rats as well! I thought I'd share that since all you rat-lovers out there might not otherwise get to see them. Here is a particularly amazing one that inspired me: http://www.guineapigcages.com/photos/showphoto.php/photo/7685. I made my rat cage with mesh grids (meant to be storage cubes) and coroplast (corrugated plastic), it's HUGE! Has anyone else built a cage? I'd be very interested to see them! It's so much fun- my guinea pigs have a 55 square foot cage!