Hi, I was lurking around autoanything website and bought a set of smoked colored door vents and I saw them selling 'Nerf Bars' for my 1990 Silverado. They say "No drilling" installation but what has been you folks tales of installation if you installed these "Nerf Bars" ? What holds them up and not damaging the rocker panels ? Thank you ! Having a h^% of a with the website today !