THanks all, I found, to my upset, that Isaly, being a labrador with a large litter, kept sitting on her pups and jumping in to feed them etc so I also want to make a slide division so they can be put safely into one side and I can then let mum in, as I found it was easier for me to wake every 2 hours, then pop them into the smaller area when finished, also it can be removed when they are much bigger. I also want some either shelve type roll bar similar to the photo above or plastic pipe (like I saw on an american site) close to the edge as the smaller rail seemed to attract the pups and they kept getting stuck, I also could cover the pipes in that insulation, the box could be fairly high sided with a bolted doorway so that the pups can use it as a pen as they get older and Jackie, I like the idea of the tent top, I could certainly do that as last time I had a unit above part of the box that I made from a chest of draws with drilled rail holes and rails. Well, we will see!