Is it the one in the main video on their site? Have you built stuff before? Just wondering cause I don't want to bore you with details if you already know this.
Looks like they built 2 frames out of 2x4s, one fits perfectly inside the other. The outer one they stapled hardware cloth to on the inside and the inner one they attached boards on the outside. The outer doors have the hinges connecting to the coop frame, the inner doors are the same except instead of connecting to the coop frame they connect to the outer D frame. I can try drawing it and posting a pic of that if you want.