Kirtles of the 15th Century

The kirtle is a descendant of the cotehardie. By the 15 century, its build was still similar in many ways to the previous century but there were changes like the appearance of a waist seam in some of them. They also commonly had short sleeves by this period, and wore the kirtles over a chemise and pinned on sleeves on the short sleeve hem. (There are pictures of the short-sleeved kirtles with just the chemise sleeves showing, but that was considered a state of undress.) There may have been other methods of attachment, but there are several period paintings that clearly show the sleeve attached with long straight pins.

The kirtles of this time showed both waists and no-waists, so you can pretty much take your pick. I usually use waist seams because it is a period kirtle construction, makes an economical use of fabric, and makes quite a bit of sense to me given the evolving tailoring of this period.