How to know. I was a witness to one case, when during a hot dispute around a broken hood of extremely exhausted alcohol men, one cried out: "Go naked! I was, fucking, an engineer!", and then disappeared for fifteen minutes in the entrance. He appeared on the street already with a welding machine. Fifteen minutes later, it was like new. And he also arrived on someone's wheel on the sides of the wheel from a small truck. The ways of drunk engineers are untold.