Chair Mat
We've got this mega monster floor mat (it's super thick vinyl and weighs 80 pounds) for the upstairs office. Took 3 people to roll the thing out. And now it's got a few hundred pounds of stuff holding it all laid out while it fights back. I'm gonna let it lay out for a couple days and let it 'relax' under all that pressure, but I don't think at this point that it's gonna be able to get flipped over and used anytime soon.