Plywood & Rubber mat question ( Who's on first )

I had plywood on top of my rubber mat and the camper moved around. I had to stop and reload the camper at one point because the tie downs were rubbing on the side of the truck. I removed the plywood (it was a support system while the camper was off the truck) and now it does not move. I would consider fastening the plywood to the bottom of the camper so nothing moves.