I used to get dozens of them in blue and black, occasionally white, from work. I used them for used oil (donated to a friend with a waste oil burner), small pieces of wood for the fire, I cut some off at 6" and use them for safety covers for deck holes (keeps rain out of the hole, too), etc. At my farm, the ground is sandy so I buried some that are drilled full of holes and surrounded by #1 stone for seepage pits for waste water and gutter drains. I might make a floating dock from some next summer. I used to take my trailer and bring home 12 to 15 at a time.