Dear site visitor:
If you arrive at the job trailer, you may be met by a lady who asks what your business is. When she finds out your affiliation, she hands you a business card and invites you into the trailer, where she proceeds to give a safety briefing on the site and an update on the status of the work. She then delegates one of the young men in the trailer to assist you with what you need.
All this activity is a signal that the lady is in charge. You should not immediately focus, laser-like, on the oldest-looking male (who is, incidentally, 10 years younger than the lady in charge) and direct all your questions to him, give him your only business card, and pretend that this lady does not exist.
Since the lady is, in fact, in charge of this particular group of workers, she has sufficient power that she can make your future visits significantly more onerous.