I have a pretty big run for my birds and it has trees and shrubs in it so I can not cover it and can not afford to get higher fence. My thought was to buy driveway marker poles and attach them to my fence posts and run fishing line across the top of the fence at about 6" this way when they hopped on top of the fence to hop over they would bump into the wire and fall back down. I don't think they could get tangled in it because it will be a single line and tied as tight as possible. My husband asked why don't I use something they can see but my thought is then they would just try and hop on the line to hop over. Part of the fence belongs to my neighbor and he doesn't mind the chickens in his yard, but we have a lot of loose dogs and I am afraid the chickens will not be able to get over the fence quick enough if one is after them.