I used a hinged piece of plywood, cut into four sections. Next time 1/4" plywood. I wonder if cutting a rectangular window in each panel, then stapling heavy mesh would lighten it up and reduce wind wanting to tip it. A cane bolt (sliding bolt on the bottom of big doors/ gates that goes into the ground, often into a pipe in ground, but not in this application) on each end might make it more stable on uneven ground.