I have a job re-attaching three of my sister-in-law's vinyl shutters on her
vinyl sided house. My house is sided with hardboard so I just nail mine on.
But I'm guessing there is only Celotex or some other lightweight sheething
underneath her vinyl that probably won't take a nail or screw. Can someone
tell me what I should do or point me in the right direction?

Thanks in advance.

Mark