Comfy privacy
These old cat litter boxes have been so wonderful as nesting boxes!
They're durable, movable, and lightweight.
In all honesty, when we first built our mobile chicken tractor, we could not figure out an easy way to factor in the nesting boxes. Building permanent boxes made the cart heavier than we wanted (I was pregnant at the time and not up for lifting much), and removed the air flow inside the cart to keep the chickens comfortable on hot days. Then, we found two old cat litter boxes.
The two boxes fit inside and could be simply lifted in and out of the cart for ease of collecting eggs. Again, I was pregnant, so bending down and reaching into the boxes would have been uncomfortable.
We used pine shavings for the bedding, but hay/straw could work or any other type of bedding. When we upped the number of layers, we added a third box, as you can see in the photo above.
Just don't tell the cat!