"My ex made a small miscalculation on an industrial part he was engineering for like a big crane and cost his company hundreds of thousands of dollars and they had to shut down. The part was for a high precision valve where even a fraction of a millimeter is the difference between something being perfect and absolutely useless.
As a web developer if that were the case in my industry I would be out of a job today."
In my country the only qualification to be a roofer is meth and mountain dew. Or an illegal Mexican immigrant. The Mexican crews don't mess around, they get that thing put on in no time. Same with brick layers.