Originally Posted by n4zou
I live in Alabama where these signs are illegal when posted in the right of way, which all of them are. Road crews must remove them when cutting the grass and that sort of thing. Your not stealing, just helping the road crews! They're also good for use between your pannier and the rack. Just cut the plastic to match the back of the pannier and tie wrap it in place on the rack. Then notch where required for pannier mounting straps. This keeps crud off your panniers and provides a nice flat surface for them.
I may have to check that out in PA law... If so, it is an interesting source of stiffening material.