Not to take away from Al's sales but for you do it yourself types, there's plans for the other kind of treadle feeder here: https://www.backyardchickens.com/web/viewblog.php?id=56638-building-a-treadle-feeder That's what I made and use. I have to lock it at night to keep Possums out of it but a brick on the upper flap does that perfectly. It's true, they will get konked in the noggin if they're not standing on the treadle and the one on the treadle jumps off, but not enough to hurt, and they learn to move their head really fast lol.