repair of boilers, the hand of the master throws and twists the nuts, close-up

appliance assistance boiler buildingservices business calorificvalue construction firedboiler fitter fix floor gas gasboilder handyman heat heater heating heatingengineering heatingplant heatingsystem heatingvalue holding home hot house housingtechnology installation installing job maintenance male man occupation pipe pipeline plumber plumbing repair repairman sanitary screwdriver service structure system tool utility valve water worker workman