Some people have their own way of doing things and no matter what you say or do they cannot be swayed. Even when it comes to their job they will insist on doing it their way. The trouble comes when they refuse to observe certain rules pertaining to the way a job is done. Some rules pertain to health and safety and cannot be ignored. A good rule of thumb to follow is to remember they hired you to do a job and trained you to make sure YOU KNOW HOW THEY WANT IT DONE. Since they are paying you to do it their way it makes sense to comply with their wishes. If you think you have a better plan for doing the job discuss it with your supervisor. Then be willing to abide by his/her decision.