I use the project boards from Hobby Lobby when they run them for 1/2 price. DH cuts then as I like them and there's no waste I fold most into thirds and they fit great. I secure them with large safety pins. The boards are white ( or black) plastic , corregated boards. DH cuts them on his table saw for me...some at 10" and some at 15" height. I can get 4 to 6 per board depending on the size I need for which ever shelf.