To be clear, most the the road side treasures come from stuff like landscaper guys, contractors, ect. I dont think I my life is have ever seen anyone strap form boards, gas cans, pool chlorine jugs, down on a trailer. It's not like the gas cans are from folks filling up an out of gas car; that would be the 1-2.5 gal. semi disposable plastic cans from the gas station.
Some of the odderer things ive found; 6 ft drill rod from a JT5 ditch witch HDD; pulling "carrots", boat anchors, plenty of hydralic fluid buckets, a single equipment trailer ramp; "hot crimp" tool for aerial power; a 16"×16"×5/8" steel plate brand new; plenty of single concrete boots; trowels: comalongs, shovels