Sewing Tip: When completing a fly-front zipper application, mark the curved placket line with hand basting prior to attaching the zipper and all it's other components. Applying this stitching guideline prior to beginning the zipper sewing process will not only allow for more precision it will also provide a lot more comfort in marking the placket line more comfortably. The hand basting lien should only be marked on the top garment layer (or side) that house the fly zipper placket in the final application. This line doe snot serve any other purpose but to provide a stitching guide later on.
Once the desired placket line is marked with basting you can proceed with attaching the facing (to the same edge as the marked placket), and aligning and stitching the zipper to the facing layer as indicated in a fly zipper application. The hand basted placket lines can be ignored during this process.
When the facing and the zipper (which is attached to the facing layer) is flipped to the wrong side of the placket, the pre-marked hand basted lines will provide the perfect topstitching guideline. all you have to do is secure all layer with pons to keep them smooth and flat during the stitching process to follow.
Starting at the top and moving towards the curved bottom, topstitch next to the marked hand basting following it carefully for a smooth, even topstitching application. This topstitch is only applied through the garment and facing ayer underneath and does not have to catch the zipper tape in the process. Remember, the zipper tape was already attached to the facing layer separately in the step above.
The importance of stitching right next to the hand basting line and not directly on top of it comes into play when the temporary hand basted threads are removed. Hand basting that is caught in the machine stitch is more difficult to remove. Conversely, hand basting that has not been accidentally or intentionally machine stitched through will be easy to remove in seconds using a seam ripper as shown above.