I have tried them all. First, a flannel-backed tablecloth. It did not work well at all, nothing stuck to it and it was too small. Then I tried a flannel sheet, then flannel yardage. The blocks would fall off if someone walked by, or if you just looked at it. Not sticky at all. Then I put up some W&N batting, and that stuff works great! I simply tacked the batting onto the wall.