​Fly Front Zipper Components And Sewing Patterns

Fly front zippers are perhaps one of the very few zipper applications taht require sewing patterns. Although at first glance, a fly front application may appear confusing and complicated to sew, once you understand its components and the purpose each one serves, you'll be able to intuitively construct a fly front zipper. ​

A fly-front zipper is used as a front closure on more casual bottoms like trousers, skirts and shorts. To construct a fly front zipper, you'll need two important components: a fly facing and a fly shield. In most cases, a single pattern piece serves both as the facing and the fly shield. Other designs require a separate patterns for both. 

In the image above, the single fly shield and fly facing pattern is drafted form the front crotch seam. This seam starts off as a straight line at at the top (which is where the zipper is attached) and extends into a semi-curved edge as it moves downward. 

A fly has a shorter structure requiring a zipper taht is only around 5". (+ plus or minus 1").  Metal chain zippers are used as they are wider and provides a heavier duty application. 

Conventionally, the fly shield is constructed of two layers while the facing is a single layer taht is interfacing and clean finished along it's outer edges. If using the same pattern to cut both the facing and the shield, you should cut two pieces (mirror image of each other) of the fly shield and a single piece for the facing. Use the pattern to also cut a single layer of fusible interfacing which will be adhered to the wrong side of the facing layer. 

Note: If you are working with separate patterns for the facing and fly shield, follow the instructions on your pattern set and these may vary. 

The fly shield is a double layer compartment with clean finished edges that is attached to the wrong side of the zipper application to provide a protective barrier between skin and zipper teeth. A fly shield can can be constructed of two separate pieces with a curved bottom edge as shown in the image above or self finished by folding a single fabric layer in which case the bottom edges will remain straight. Before attaching the fly shield to the fly zipper application, all edges except the top horizontal one, should be clean finished.

The fly facing is cut from a single fabric layer often featuring a curved bottom, used to clean finish the zipper placket opening. The fly facing should be interfacing such taht it provides the much needed structure and strength in the completed zipper application. 

If you take a look at an open fly application, you'll be able to easily spot the fly facing and fly shield. The facing is locate don the wrong side of the zipper placket as shown above. There should be a seam taht connects the facing to garment at the placket edge. 

The fly shield is the double layered portion located at the vary back of the zipper opening. When the fly is open, the shield appears as an extension located underneath the zipper teeth. On the wrong side of the application, the fly shield should completely cover the zipper teeth/tape when the zipper is in closed position.