@84GMCSierra Ok so we are going to start with talk about the front and the pinch weld attachment because that seems pretty universal across all boards, the center and back tend to vary a little so I'll talk about that when we get there.
Front is simple a plate that bolts to the fender, and then to the board.
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My boards use 5 bolts through the pinch weld. I drilled and bolted the pinch weld, then did the front plate center support then rear, leveling the board as I went.
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Center support, below: Mine bolted to the existing holes on the boards and then to the rail on the cab floor. I have seen some where the center support goes to the frame.
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I'll do the rear in my next post as I had issues with it.