I use aspen shavings as substrate in my racks, and then the snakes can just burrow under it when they want to hide. I used to put actual hides inside my racks with the aspen substrate, but I found my snakes didn't really use them that much for hiding, but they did like to poop all over the edges of them, making me constantly have to clean them. So I stopped using them, and everyone seems perfectly happy now with aspen and no hides.