The trench coat is one of the few garments where nearly every detail began as a function. Designed for officers in the trenches of the First World War, it carried features for weather, equipment and rank, and those features survived into civilian fashion as recognizable signatures. Reading a trench coat is partly reading its military history.
This guide names the distinctive parts of a classic double-breasted trench and explains what each originally did. Whether you are drafting one or simply appreciating the design, the coat makes more sense when its details are understood as solutions rather than decoration.
The double-breasted front and its closure
The classic trench crosses a wide double-breasted front, usually with ten buttons in two rows, giving a broad overlap that seals out wind and rain. The generous wrap is not styling for its own sake; it doubles the fabric across the chest for warmth and protection in bad weather.
A convertible collar lets the coat be worn open and relaxed or buttoned high and closed against the elements, with a throat latch or hook to secure it. This adaptability is central to the garment's original purpose.
Weatherproofing details
- Storm flap: an extra panel across the upper back or right chest that sheds rain away from the body.
- Gun flap: the chest flap, originally cushioning a rifle butt, that also directs water off the front.
- Raglan or set-in sleeves with a storm shield at the shoulder to keep the seam dry.
- Cuff straps: adjustable tabs that cinch the sleeve to keep wind and water out at the wrist.
- Yoke and back vent: a caped back layer that lets rain run off clear of the coat body.
Pro tip
The traditional trench fabric is a tightly woven cotton gabardine, water-resistant by weave rather than coating, which is what made the original coats both breathable and weatherproof.
Military hardware and details
Epaulettes, the shoulder straps, once held rank insignia, gloves or a whistle cord and now survive as a defining decorative feature. The belt carries D-rings at the waist that originally attached field equipment such as map cases or grenades, though few wearers put them to that use today.
The buckled belt itself cinches the waist and can be tied rather than buckled for a softer line. These pieces of hardware are what most immediately identify a coat as a trench rather than a plain raincoat.
The back, vent and length
A classic trench falls below the knee, long enough to protect the legs while allowing a stride through the deep back vent. The vent, often buttoned, lets the wearer walk or ride while keeping the coat closed against the weather. A back yoke and cape shed rain clear of the body.
The length and vent together are practical choices that also give the trench its characteristic silhouette: long, belted and slightly military in bearing.
Drafting a trench and keeping the details true
A trench coat pattern is demanding because the storm flaps, gun flap, epaulettes and belt loops all have to register precisely against the body panels, and the double-breasted overlap must be exact for the buttons to align. Accurate placement marks matter more here than on a simpler coat. Minerva Patterns supplies coat patterns in DXF AAMA, PLT and PDF with placement drill holes for these details, drafted to individual measurements so the overlap and belt sit correctly.
Frequently asked questions
What is the storm flap on a trench coat for?
The storm flap is an extra panel, usually across the upper chest or back, that channels rainwater away from the body and the seams beneath it, keeping the wearer drier in wet weather.
Why does a trench coat have D-rings on the belt?
The D-rings are a military inheritance. They originally let officers attach field equipment such as map cases or grenades to the belt, and they now survive as a recognizable design detail.
What fabric is traditional for a trench coat?
Tightly woven cotton gabardine is traditional. Its dense weave makes it water-resistant while remaining breathable, which is why it suited a weatherproof coat meant for long wear outdoors.
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