Here is a picture of a flight pen like Oldtimr is talking about that shows how the posts/poles hold the net up at least 7-8 feet high at those points. Definitely put the wire down into the ground along the sides a couple feet if the ground is easily dug and maybe a foot or two horizontally also, as that really slows a varmint down when it digs and then comes up only to hit that wire. IMHO it's even better to run that horizontal wire out away from the pen. Then a varmint has to figure out that it needs to start digging way away from the side, whereas normally they will start right at the fence itself and go down only to hit that horizontal wire. All it takes is one fox or weasel to get in and they will kill every bird in one or two nights and it's not a pretty sight to see! Good luck with the project and when you're done maybe post up a picture or two.