Steeking pleats
A well-made kilt will have the under-pleats steeked *. Steeking (or "lifting") stabilizes the under-pleats to prevent them from sagging with time and producing a saw-edged look at the selvedge. Because it is time consuming, some kiltmakers skip this procedure. But time will tell the tale.
After steeking, the pleats are basted and pressed into their new positions.
* Steek: A Scots word meaning to shut, close, fasten down or lock up. Dates from the 13th century.
Does your kilt need steeking?
A kilt that has been properly steeked will have a sturdy line of hidden sewing across the pleated area of the kilt. The steeking can be detected by gently running your finger up the under-pleat up to an inch above where the fell stitching starts. Without steeking, you will be able to run you finger well past that point for the whole width of the under-pleat.