A Simple Fly-Front Zipper | Video
Many pant styles, from jeans to trousers, call for a fly-front zipper. Author and teacher Pamela Leggett demonstrates her simple, foolproof method for sewing this type of zipper. You’ll adapt the pants front pattern, cut and mark the fabric, baste, press, and then install the zipper. After topstitching the overlap side, you have the option of adding a zipper shield. Each step is easy to execute and, in every case, you can go back and redo a step if you’re not happy with the results.
Adapt the pattern
Begin by assessing the pants front pattern. The pattern must have a fly extension. This may be attached to the pattern or intended to be cut as a separate piece and sewn to the pants. Pamela advocates for the cut-on extension style, as it reduces bulk over the lower abdomen. She describes how to add an extension to a pattern that doesn’t have one, so you can revise your favorite side- or back-zipping pants to add a fly zipper if you prefer.
Prepare the pants front
Cut the pants front and apply markings: You’ll mark the center-front line, the crotch curve, and the dot that indicates the bottom of the zipper.
Then clean-finish the cut edges. It’s impossible to serge them after the zipper has been installed, so you need to serge or zigzag them at this stage. You’ll learn how to negotiate the inside and outside curves at the bottom of the zipper extension.
Finally, stabilize the extension with a strip of fusible interfacing. A product Pamela recommends for this is Knit Stay Tape/Interfacing, by SewkeysE. It is 1 1/4 inches wide, so all you need to do is cut it to length and fuse it in place.
Install the fly-front zipper
Begin by basting the center-front seam from the waistline to the dot; backstitch at the dot, then continue sewing with a normal stitch length (about 2.5 mm) to within 1 1/2 inches of the pants inseam intersection. Press the fly extensions open.
Choose a zipper that is longer than the zipper opening. This makes it easier to sew, and you can cut off the extra length at the waist end after the waistband has been attached.
Next, machine-sew the zipper tapes to the fly extensions. Pamela’s method doesn’t call for measuring where to sew the zipper: The center-front seam, zipper, tape, and bottom stop provide the guides you need for perfect placement.
Flip the garment right side up. Press the front. It helps to slip paper between the pants front and zipper to prevent the zipper teeth from creating an impression on the front.
With a pin, mark where the basting stitches end, and mark the zipper stop with another pin. These are important landmarks for topstitching. Then mark the topstitching line with a strip of cellophane tape. You won’t need to apply chalk or other marker to the pants front, so there is no risk of having marks that can’t be fully removed. Another option is to use a freezer-paper topstitching template.
For the topstitching, set the machine for a longer-than-usual stitch. As you sew, be sure to sew around the zipper stop, to avoid breaking the machine’s needle. After topstitching, remove the tape and the center-front basting stitches. The basic fly-front zipper is complete.
Add a zipper shield
For jeans and sporty pants, you may want to include a zipper shield. You’ll learn how to make and insert one of these, without a pattern. Once the shield has been added, sew some bar tacks to secure the its lower end.