There's no need for them to be "D" shaped. The water doesn't care. Just drill a few holes to just miss the inside skin. I think that the skin was punched at the factory and the flaps left in place to locate the outer skin against the inner before folding the edge over the inner skin.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.