I agree, lids are always a good idea! You'd be surprised just how smart hams are, I've seen them pile all their bedding up on one end and simply walk right out of their cages. They're also good for your hamster's safety, young children or other pets could easily reach in and harm or scare your hamster and you definitely don't want that. Lids are fairly easy to make, simply take steel mesh/hardware cloth and cut to size so it fits over the detolf