I made a blanket sort of for my dog that likes to get way down under the blanket. Also my daughter used these for her farrets. That is where i got the idea from a ferret catalogue. I made a retangle blanket and folded it in half sewed up one short end and the long end. Then on the other end I sewed polyester horsehair braid. It will keep the opening where they crawl into the sleeping bag open. You just have to remember to make it deep enough.