ok they are all called the hagen vision thats the model here is a picture how we all set up the doors to open outward into a drawbridge...see also LANES post ...

he had a great idea of instead of using common white string he used the small lamp chains you can buy in any hardware store...
this is when i just weaved the white string thru both the doors ...works great just when closing doors make sure any excess string is OUTSIDE the cage...

lanes idea is even simpler and looks neater too.