OK, I know this has been covered, but a search didn't unearth anything. I am building a 3 hole nestbox out of OSD that we got really cheap at Home Depot last weekend. The unit is 36" long x 12" high and is divided into 3 areas. I have the bottom back and dividers in place. the top will lift off for cleaning. Now the question. How big should I cut the holes for the girls to go in to the boxes? I have the 36x12 piece cut, but I'm not sure how large an opening they would need (or want). their existing nest box (in the old coop) is about 10x10 and pretty much the whole front is open. Anybody have any suggestions about size and shape? I'm getting pretty good with the jig saw (just don't ask me to use that scary table saw ;-) ).