How to put fleece on cage shelves?

I just cut 2-3 layers to fit the shelf and then safety pin them to the bars. Your rats *might* chew it off the safety pins but I haven't had a problem with mine. And a tip; you should vacuum the fleece daily to keep feces and junk off. If there's junk on it and they pee, it's pretty much stuck there and ends up having to be trashed.