A house for rats (or other rodents). DIY: 1. You'll need a closed X-ray box with a hole in one corner, a sharp knife and a glue gun. 2. Saw the box in half. Saw off the two large sides in the half without the hole in the corner. Maybe saw the hole in the corner a bit wider as well (I did that). 3. Glue the two sides on top as a roof. 4. Give it to your rats.
Some rodents need a sand bath. I made this for my chipmunk Peanut. DIY: 1. You'll need an empty 2 liters ice cream bucket, some duct tape and a sharp knife. 2. Cut the top off with the knife. (Just throw the top out. You won't be needing it.) 3. Put duct tape around the edge so the rodent won't cut himself. 4. Fill it with chinchilla sand.