I have one very smart Leghorn (my favorite) who used the nest box almost from day one. She has gone back to it ever since. I thought, "great! She is starting everyone off right", but the rest of my mixed flock has been laying on the floor or in FRONT of the boxes. Silly girls. I have two boxes of ample space up on stilts about 18", but no roof or sides. I have golf balls in it too. My Leghorn uses the shelf unit I put in on its side, and loves it. I am going to give the rest a few more weeks and then probably put a plastic milk crate in the other open nest boxes to see if that helps, because right now the girls go in, but just scratch the straw around.