We used 1/2 inch squared welded wire cloth on the sides. That will keep out almost anything, including predators, diseased wild birds and wandering dogs and cats. The wire is also stapled at the base of the coop, bent down with 6 inches extended on the ground to prevent digging under. The wire on the ground is also covered by pavers around the base of the coopfor an additional layer of protection. The 6 inches of mesh around the wood bottom of the run will eventually be covered with cardboard, dirt and will be turned into a herb garden to repel insects and pests.
The top of the run is covered by a heavy duty shade cloth that will not only provide shade and protect from hail and harsh weather, it will also keep the hawks from getting in. You can get different weaves of shade cloth depending on how penetrable you want the fabric to be.
Have a little more work to do, but nothing it too good for our chickens’ protection.