I use these two boxes to separate the cocks and hens for flying. In the beginning of the flying season I have more flyers than I need for my flying kit so I keep a reserve of flyers to replace members of the main kit in case I lose some to falcons or they drop out for other reasons. Since the hens don't need individual boxes, I can use one of these boxes to keep my flying hens in to make room for flying cocks to have their own individual boxes.