It's wood, or more accurately plywood. It comes in 4 foot by 8 foot sheets in varying thicknesses. Kinda surprised you didn't know that.
Oh, you mean the genius idea.
You ride your bike up to Lowes. Buy a 4x8 and take it out to the parking lot. Then you lay it long ways beside the bike with the long edge against the tires.
Then you lean it up on the other side. This replicates the bike leaning so you can see what is going to drag first. Make any adjustments as needed. I was looking for a comfy spot for the highway pegs that gave me max lean.
When you are done you return the plywood to Lowes and ride home.