This is a "Florida Chicken Tractor". It's nothing more than a portable, roomy pen with an open bottom. The open bottom allows the birds to get at the weeds and bugs in the lawn. At the same time, they are fertilizing a 4 x 8 foot section of the lawn. The pen is moved a couple times a day, typically once in the morning and once in the evening. There is a good book, "Chicken Tractor", by Andy Lee and Pat Forman that details different types of chicken tractors. Mine is pretty simple, but it works. I am going to add some old lawnmower wheels to make moving it even easier.These chickens are technically "free range" birds. Any freer and they'd probably be dead by now from the raccoons, foxes, and coyotes that pass through my woods. The white rooster in the center is "Gandalf". When frightened he runs in tight circles...he'd be toast if allowed to run free. He's been working on his crowing though and it's getting better.