I was fortunate enough to acquire a massive amount of plastic 'cardboard' - the kind you see on wired stands stuck in the ground - they're usually used for advertising a person running for local political office. My neighbor won the election, threw all of his signs out on recycle day, but I got to them first. I washed them and cut them down to size (6 x 9) and now my Ikea shelving (Expedit and 2 Billy Bookcases) look amazing!!!