What Is A Lapped Zipper Application?
A lapped zipper application is one of the most widely used zipper closure in dressmaking. You can easily spot a lapped zipper by identifying a single topstitched or hand stitched placket on one side of the seam. Conventionally, the placket is located on the seam's left side. If you open the zipper, you should also see a topstitch applying along the folded seam edge opposite the edge housing the placket (as pictured above). When the zipper is closed, this topstitch is hidden underneath the zipper placket.
On the wrong side of a lapped application, the zipper will sit directly on the seam allowance layers and all topstitching applied on the face of the zipper application should catch each corresponding zipper tape portion.