My friend made me nest boxes from an old shelving unit and milk crates. He cut down the crates at an angle and placed them on the shelf. If I had to do it over, I would have put the crates on the shelf sideways & I would have put a lip on the self. The more privacy the better. I ended up trading out a couple of the crates for old dresser drawers. My hens like a larger, communal nest.
