When I had chickens back in the 90's we built a structure we could move around in the yard and my chickens could be on the grass and eat bugs and all the perks of being free-range and none of the preditor dangers (there were woods full of coons, foxes, hawks, etc all around us). Our little cage (I didn't know it was called a "tractor" until a couple days ago!!) worked great! I've been looking at plans on how to build one online and I notice most of them don't have a bottom in them! My question is: How do you keep the critters out and the chickens in without it being totally enclosed? Do they get tied down or do they usually have stakes that go in the ground to hold it down, or what?? And how do you get the chickens from the coop to the tractor without turning them all loose? TIA for any help you can give me!