Ratties like to have a hiding spot. Plastic tubes or plastic pet store shelters are great, but you can also just give your ratties an empty box your own food came in. Something like an oatmeal tube, a cereal box, instant mashed potato box, you get the idea... and my ratties wanted me to tell you to leave a little food treat in the box for them to find on their own. I change these boxes daily or every other day.
In the high plains of South Dakota, USA