Lowering A Model A Lid, Part 1 - Chop Top Basics Photo Gallery
 Since the A-pillar is tapered it can be difficult to join the outer skin without pie cutting. This way we can remove a little material on the removed piece and fit it in without a seam in the middle. But the most important reason is because of the structural metal under the A-pillar skin. Unless you remove it, you will not be able to join these parts for a proper strength. Now you can weld it up solid for strength.