my design wall is 1/2" styrofoam glued to a wall with just 'dots' of construction glue here and there so when it has to be removed it will be possible to clean off the glue easily. then i used spray glue on the foam...and pressed 72" poly felt (it's not real anymore) onto the foam. the foam comes in 4 x 8' sheets so i got 8 x 8 with 2 pcs and needed 2 lengths of felt to cover the whole wall section. i thought the felt was a little too smooth so i used a scrub brush to bring up the nap and it works great. I think it isn't as 'nappy' as wool felt in the first place, but i think a lot of the nap was just crushed on the bolt... brushing it worked great and if something is getting too heavy as more and more blocks are joined, i can always pin into the foam....