There's a number of ways to pleat up tartan into tailored kilts. A distinctive pleating method which applies specifically to regimental kilts is the military box pleat. Not to be confused with the 5 yard box pleat kilts widely worn throughout the late 18th and 19th centuries, the military box pleat is an advanced kiltmaking skill.
Military kilts are different from knife pleat, civilian kilts from the out set. They are traditionally created from specifically regimental cloth weighing 21 oz per yard - significantly heavier than standard kilts. The texture of this tartan differs too - it feels brushed and looses it's obvious twill as compared to medium and heavy weight tartans at 13 oz and 16 oz per yard. There is also a limited number of tartans woven in regimental weight, reflective of the traditional highland regiments - Gordon Modern, Black Watch, MacKenzie Modern for example.
There are other details which set military box pleat kilts apart before even getting to physically pleating. They often don't have sporran loops and can be made from as much as ten yards of cloth. Military kilts are always pleated to the stripe. This means a stripe central to a band in the sett is chosen to form the centre of every single pleat. For example, the gold stripe of the Gordon tartan (illustrated) may be chosen to form the centre of the pleat. The front and back of the kilt will therefore look extremely different - primarily dark blue and green on the front apron, but when the wearer turns a, now, predominantly dark green and gold tartan is revealed. This kilt, although a knife pleat kilt, tailored for Strictly Come Dancing contestant JJ Chalmers, is a beautiful example of the striking method of pleating to the stripe in Cameron of Erracht Modern tartan. This was done as a nod to his time serving in the British military.
The pleating is where the military box pleat really stands out. It is a tricky and highly skilled task to form the box pleats and is done in a number of stages. First of all, the kilt's aprons are formed as would happen with any kilt - now things start to change. Rather than pleating up, as you would with the stripe normally, from the front apron to the under apron, the cloth is instead pleated from the under apron to the front apron. This, to the kiltmaker, is like working back to front as you would with a women's kilt. Once the fell (the sewn third of the kilt) is handsewn, the pleats are all individually folded back on themselves to form the "box" (again, this is not the same as 18th century 5 yard box pleats). Working from the under apron to the front again, the pleat is folding to create a new edge and each is tacked in place in pressing. Each pleat then consists of 4 layers of heavy cloth and swings in more of a back-and-forth motion instead of brushing side-to-side.
The kilt featured was created by an Edinburgh Kiltmakers Academy. EKA teaches military box pleat kiltmaking to advanced kiltmaking students. It is rare that one is ordered largely because the military now recycles kilts as much as possible and for civilians wearing to special events, they are exceptionally heavy. For a kiltmaker though, it is a wonderful skill to possesses and truly pushes their attention to detail and meticulous pleating knowledge.
Regimental kilts are both complex and beautiful. They are designed to last, even kilts which have survived the trenches of WWI have made their way into the wardrobes of today. To create a beautifully made military box pleat kilt is a great achievement for the kiltmaker, and although rare, they are a challenge and a reward to make.