My husband got some scrapped pieces of rubber coal conveyor belt free from the plant. I drag a couple of those around to kill weeds. They get really hot when the sun shines on them and they're heavy.I'll tell you what Does work--rubber mats. If somebody has some old exercise mats that they don't want anymore--the kind that weigh nothing and jigsaw puzzle together--you'll kill anything underneath them. I'm not sure that the plastic really works to kill anything.