Tim Allen's current thread concerning a flag of the 5th Company, Washington Artillery, raises a question in my mind concerning the proper "seamtress's terminology" for describing the process or result of cutting away a part of a flag and replacing it with another piece of cloth to avoid having multiple-ply fabric -- or, in Tim's case -- a lighter color(white) being stitched over a darker color (dark blue).

I have encountered this construction in US Army Signal Corps flags -- the familiar red square on white field, white on red field, etc. -- which, I am reasonably certain, are post-Civil War ... perhaps Span-Am or even early 20th Century. Unresolved is how early this practice was adopted and whether it was in use on wartime flags of the first generation signal services, north and south. But what should it be called?

Example, white field: space for the center red square is cut away, a square of red material is stitched (double-stitched, machine) to cover the "hole" while retaining single ply. The term "inset," or "insert" comes to mind, but I'm uncertain whether that is clear or proper -- whether it should be sought as keyword in specification or contract work, in instruction to the maker. Could someone enlighten me on this, so I don't have to explain all the time when I want to describe the feature?