Side zip, back zip or fly front: women’s trouser openings

The three openings compared

All three can be neat; the choice is about the look and the wearer.

• Side zip. A zip set into the side seam, usually on the left, often an invisible zip that disappears into the seam. The front and back stay completely smooth, so it suits flat-front, slim and cigarette trousers and anything worn with tucked-in or short tops. It is a little harder to reach, and a side zip under a fitted top can show a slight line at the hip.
• Back zip. A zip in the centre back seam. Common on skirts and dresses, less so on trousers. It keeps both front and sides smooth, but you need to reach behind you, and it takes strain when you sit.
• Fly front. A zip at the centre front behind a stitched flap, closed at the top with a button or a hook and bar. This is the jeans and classic trouser opening. It is the easiest to use, works with belt loops and pleats, but adds a visible line and a little bulk at the front.

Which suits which trouser

Smooth, minimal trousers and anything worn with a short or tucked-in top usually look best with a side zip. Tailored office trousers with belt loops and pockets often have a fly, especially with front pleats; our guide to pleated or flat-front trousers explains how the two go together. Skirts and dresses mostly use back or side zips.

Under a long kameez or kurta, the opening is hidden, so comfort decides. Many people choose an elasticated waist with a flat front panel, or a fully pull-on straight trouser, and avoid zips altogether.

Small details worth deciding

The fastening at the top of the zip matters as much as the zip. A hook and bar holds a waistband flat and takes strain; our article on the hook and eye explains the difference between the two fasteners. A button adds a visible detail, often used on a fly. An extended tab can close over the top for a sleek look.

Also think about pockets: side-seam pockets sit awkwardly with a side zip on the same side, so the zip and pocket are often placed on opposite sides, or the pocket is slanted on the front.

Ordering the opening you want

Our quote form lets you choose the trouser style; add the opening in the notes, such as “invisible left side zip, hook and bar at waistband” or “fly front with button”. If you are not sure, say how you will wear the trousers and we suggest one. Give your waist, hips and rise as shown in the trouser size guide, and see trouser fit for how rise affects the waist.

Send it through the quote form. Custom stitching describes the process, and the opening and fastenings are agreed in your written quote before cutting.