PL Parking Stops Dress up the appearance of your parking lot while contributing to a cleaner environment. PLC Parking Stops never need painting. They won't chip, crack or deteriorate from weather or road salts. Installation is simple. Rebar fasteners included. What is plastic lumber made of? It is made from recycled plastic milk jugs, otherwise destined for a landfill. When using plastic lumber, you are helping the environment as well as utilizing a long-lasting, maintenance-free product. Quantity