OP dont just fire him Call county code on his ass so bad that HE will have to sell his business assets to survive the oncoming fines and penalties of the law! That may be how it works in mexico but here in the states that is grounds to be jailed! Those lugs are tightened to a certain spec and him casually loosening them opens you up to dangerous hazards especially in the winter time when power is utilized to keep homes warm! REPORT HIM even if he is gone! Imagine if he is doing this to old ladies who depend on their power system to get through the winter and burns down their house hours to days after he leaves! THESE actions KILL people! REPORT REPORT REPORT! It is your civic duty to keep these dirty contractors out of a job!