I use the rigid insulation board - 1" thick. Had them cut it in thirds so I could get it home in my car. Used 1/3 of it making an extended table for one of my machines. Taped the rest together & used T pins to attach it to the wall. I bought a design wall thing (plastic grid on one side and flannel on the other) and it's pinned to the insulation board. I can pin a good sized quilt top to my design wall because when it gets too big it won't stick to the flannel.