We use two pieces of corrugated polycaronate (
http://www.mcmaster.com/#corrugated-...sheets/=gnf1k0) refer to the image labeled non-corrugated. it is also called corriboard or corrugated plastic. We use two 1/8" thick pieces with the channels running in opposite directions. use srews or bolts to attach. We use an ice pick or pin to poke a hole where we want the screw to go, and then use 10-24 bolts, not screw, to attach. They tap themselves into the plastic, and the connection is sturdy without a nut as long as you dont detach and reuse the hole many time. Good Luck! Hope to see it in action next year!