What Are Zipper Underlays And Why Use Them In Dressmaking
A conventional zipper underlay is a single or double fabric layer compartment that is stitched to the wrong side of some zipper applications to provide a protective buffer between the zipper teeth/tape and the skin surface. Particularly when working with metal chain zippers or when sewing fly-front application (pictured above), underlays provide an imperative role in providing comfort and full garment functionality.
A zipper underlay should be wide enough to fully cover the entire zipper including both zipper tape edges. Most zipper underlays measure anywhere from 2-3" in width. Not only should they cover the zipper fully, the should also be stable and structured enough to remain properly aligned during the garment's life cycle. Underlays are usually attached to the wrong side of the zipper application, after the zipper is fully stitched. The underlay's vertical straight edge is stitched to one of the seam allowance edges housing the zipper. The open bottom corner is conventionally tacked down to encourage the underlay to lay flat and remain in its proper position during wear.