I was browsing ebay and I found someone on there selling homemade C & G cages. This person has doors on that open with a spring, but I cannot get the pictures zoomed in enough to see how she made them. I have to have complete enclosed cages because of a toddler and cats. I would love to figure out this hinged/spring type door, instead of just using zip ties to open the top of it. I can get the link to the ebay one I saw. I want to build my own but I would really like this tpye of door.