My chicken pen is a chain link fence 20 x 30 I built many years ago. It now houses my chickens. Since Jan 2023 I have killed 4 possums in this pen. They were trying to get at the hens. In a effort to deter the little bastards I'm trying this. Carpet tack is cheap and filled with thousands of little thorn sharp nails at an angle. I first soaked the carpet tack in used motor oil to protect from bugs and weather. I then zip tied the pieces to the top angling the nails outward. Nails are sharp as I put a few holes in me installing them. We shall see if this works.