Not a stupid question at all. You can buy cardboard (chipboard) at www.uline.com
, or go to a printing place, they use large sheets as backing for tablets. I buy mine from one of my suppliers, but it's getting expensive. They make me buy 50 pounds at a time, and it costs $80.00. For patterns, I use 30 thousandths thickness For the sun visors I used 40 thousandths thickness.