Tutorial: How to Sew Pan Covers for Ferret/Critter Nation Cages / Rat-related comment: Covering the rats' Day Cage during daytime encourages them to be active. Also see aromatherapy with grapefruit scent.
You'll have a wonderful crop of grass'' in under a week. Cut a difficult parcel of fabric to size. You might locate these free somewhere, or they're just a few dollars to purchase new. Then there's the extra bonus of locating a treat.
DIY: Guinea pig cage that was a TV unit in a former life. A ramp connects the 2 levels and there is a sheltered sleeping area plus lots of storage. The guinea pigs' favourite spot to sit is right in the middle of the ramp.