I used the 1" thick insulation board that can be found at Home Depot. I covered them with flannel and used safety pins and twine to keep it snug onto the insulation. I had three of them before my move. Now I have ONLY ONE because for some unknown reason, two were put into storage. I have had to temporarily hang a peace of batting taped to the huge closet door. You will find that the insulation is great because you can use straight pins! I can't wait until my other 2 design walls finally get moved into my new apt.