you just have to use whatever works for you. For me the cheaper the better! I have a year old albino burmese in a tub (LARGE tub) with latches on the ends and was concerned, as you are, about him pushing it open in the middle, so what I did was to take the spare 17" computer monitor I have sitting around and put it on top of it. If he can get that moved, I would be seriously scared of him!! I've seen books, cinder block halves whatever has weight to it used. Another thought would be to find the right length bungee cord with hooks on it and wrap it around and hook it to itself. That should keep it secure.