How to sew a zipper fly

This post is a visual help to complement the sewing instructions for our PDF sewing pattern for boys and men's Pants and Shorts #2107. We use bright fabrics with contrast thread to help you better visualize each step. In order to have smaller pieces on the photos, we show you the front pieces that have not been sewn to the back.

Getting your front pieces ready

The very first step before you start your project is to transfer all markings onto the fabric. The most important mark for the fly is the dot you will find at the front crotch, just above the curve. Make sure it is visible on the wrong side of your front pieces:

JALIE-2107-1 - Mark crotch mark before you sew the fly

You can finish the edges with your serger before sewing to minimize fraying.

Front crotch seam and fly facing

At step 23 of your sewing instructions, pin and stitch front pieces together, from the crotch mark to the inseam, 1 cm (3/8'') from edge:

JALIE-2107-2 - Sew crotch below fly opening

Mark or clip your fabric 1.5 cm (5/8'') from edge, at top edge (step 24). This indicates your center front, where your fronts will meet at the end. Use your paper pattern as a reference to transfer the mark:

JALIE-2107-3 - Mark center front at waist edge

Pin right side of fly facing to right side of left front and stitch, from the waist mark to the crotch mark (where your crotch seam starts) (step 25):

JALIE-2107- Sew fly facing to front (view front right side)

View from wrong side:

JALIE-2107-Sewing the fly facing (wrong side view)

Open, bring seam allowance towards the facing and understitch (stitch close to the seam) (step 27).

JALIE-2107- Understitching the fly facing


Inserting the zipper

Pin zipper, face down onto right side of right front (the front piece without facing), with the zipper stop at the mark, and stitch on the zipper tape, stopping when you reach the bottom stop (step 29): 

JALIE-2107-Sew one side of the zipper to right front

Bring left front over the zipper, its edge against the mark on right front piece (step 30):

JALIE-2107-Fronts ready to be overlapped
JALIE-2107- Join left and right fronts at the mark

Pin close to the mark, through all layers (step 31):

JALIE-2107- Bring centers together

Bring left front right sides together with right front to expose the zipper and facing. Pin the zipper and facing to keep them together. Then, flip your pieces so that the zipper is on top, as you can see on the second photo:

JALIE-2107- Pin zipper tape and fly facing
JALIE-2107-Free zipper tape pinned to fly facing

Stitch on the wrong side of the zipper tape, through the zipper tape and facing and stopping when you reach the bottom stop (step 31):

JALIE-2107-Sew your zipper to the fly facing

Fold up the zipper tape so it does not get caught in the topstitching later (step 33):

JALIE-2107- Lift your zipper tape before topstitching


Topstitching the fly and adding the fly shield

On the right side of left front, trace your topstitching line with tailor chalk or soluble marker. Start with a straight line, 3 cm (1 1/8'') from center front and finish with a curve that will end at center front. Topstitch on the line, through all layers, then remove the pin.

JALIE-2107-Mark the topstitching line for your fly
JALIE-2107-Topstitch on your mark through all layers

Fold the fly shield lengthwise, right sides together, stitch across the end and clip the corner (fold) (steps 36-37):

JALIE-2107- Prepare fly shield

 Turn right side out, press and topstitch along the fold (step 38). You can finish the raw edge with your serger:

JALIE-2107- Topstitching the fly shield on the 2107 men's pants

Pin the zipper to the fly shield, raw/serged edges together (step 39). At this step, the zipper is sandwiched between the fly shield and fly facing: 

JALIE-2107-Pin zipper to fly shield

Baste with a zigzag first  and then sew with a straight stitch (step 40) through all layers: 

JALIE-2107-Sew zipper tape to shield - view from wrong side

Open the zipper and baste with a straight stitch as shown in the photo below, 1 cm (3/8'') from top edge to create a temporary stop (steps 41-42). The photo shows the first stitch. Repeat for left front:

JALIE-2107- Stitch across the zipper tapes

Cut excess zipper and sew two bar tacks (steps 43-44).

JALIE-2107-22- Bar tacks to finish the zipper fly


We hope this will give you the confidence you need to tackle a sewing project for pants, jeans, trousers with a zipper fly. The sewing technique used in other pants patterns like the women's 2908 - Stretch Jeans Pattern or 2909 - Classic trousers pattern may differ.

Keep in mind that you can, before buying any Jalie sewing pattern, access and read the instructions to see which techniques are used. Simply click "View Instructions" under "Details, Sizing and Instruction" on any pattern page.

Whenever in doubt, don't hesitate to contact us or share photos of where you are stuck in our positive and helpful sewing group on Facebook

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