A few years back, I hired a contractor to replace my barn roof. He subbed the job out to an outfit that used day laborers who spoke no English. They showed up on the windiest day of the year and spread a large tarp on the ground to catch nails & debris as they stripped off the old roofing. I tried to tell them the wind would pick up the tarp but they had no idea what I was talking about and just kept on working. Sure enough, a few minutes later, a gust of wind lifted the tarp and scattered the nails & debris all over the adjacent field.
My wife and I spent the next week with a metal detector and bar magnet cleaning up the mess the crew left behind. We picked up a 2 gallon bucket full of nails and other metal pieces.
If it weren't for the metal detector, I'm sure my tractor tires would have found them!