Weatherstriping Question?

[dvldog 70k5]

I am trying to order all my rubber for my Blazer before I paint it and I dont know what the diffrence is between sing and double wall is. I also dont know how to tell which one I have.

Nick

 

[spearchucker]

The double wall bolts up from the bottom with the nuts in the top itself and the single wall have the bolts visible on top with the nuts tacked to the bedrail.