Quote Originally Posted by ForresterModern View Post

Fell: the sewn together portions of the pleats at the upper few inches of the rear pleated section of the kilt, shaped so as to make the fit of the kilt tailored to the wearer's waist and hip measurements
Conventionally, the fell is one-third of the overall length of the kilt. I suppose one might modify this to match the maximum circumference of the hips, but a third is usually spot on.
Reverse pleat: typically slightly deeper pleat at the left margin of the front apron that has its edge facing rearward, or reversed to all the other standard knife pleats, adds extra mobility to the pleats without distoritng the apron
ForresterModern, you seem to be speaking of the viewer's left? That would be the wearer's right, the edge of the underapron. This reverse pleat, together with the last knife pleat, forms a box pleat which (as FM says) nicely accomodates motion of the leg. Likewise:
Deep pleat: the first knife pleat on the wearer's left, at the edge of the apron, is made a little deeper than the others; for just the same reason, ease of movement.

As DrummerBoy suggests, Barb and Elsie's book will answer all these questions, and more. IMHO every kilt wearer should consider buying this book, which will help you to evaluate any new or used kilt you consider purchasing, and to understand and appreciate the kilt you have. Celtic Dragon Press is Barb's Web site.