Quote: I think the golf balls help. Very rarely have I had the birds lay outside of their nest boxes.
I agree. I have used milk crates in the past. I have put a piece of wood screwed on to hold the hay in but now I just set the milk crates upright whenever I use them and the birds will get in them and lay. Plastic wash tubs work well too. You can use most anything. I have seen people use old dresser drawers.Milk crates make a good nesting box but work better if you add a lip on the front to hold the hay or chips in.