It is easy if you see what is done - just explaining it seems complex.

At the edge of the apron there are two folds at the waist level but only one at the bottom edge.

Looking at the edge of the apron, at the waistline, from the outside of the kilt, the edge is shaped by being pushed into a W shape up to two inches deep at the waist, but that decreases until it ceases to be a fold and is just the edge of the apron, a single fold. You would be able to push a finger of your right hand into that small shaping fold if it was not already tacked together.

Behind the two folds of the shaping there is a large pleat intended to allow free movement and for the aprons to drop between the thighs when sitting or to allow the aprons to stay together when getting over a gate or style or riding a bicycle. Usually the lower edge of that large pleat will drop down below the level of the apron. Normally that is hemmed to prevent it showing, but I find that there is a problem with the pleat tending to roll outwards. I have been making clothes for a long time and decided that pulling the inner fold up just a little would solve the problem, which it does. Other ways to resolve it are to sew several lines of stitching along the inner edge drawing it up as you do so, then press - that would only work for wool or wool blend fabrics which could be tailored, or sewing a strip of cotton tape to the inner fold and then shrinking it with a steam iron.

Anne the Pleater. :ootd: