It is a flat strip set alongside a seam so it looks superficially similar to piping, and has the advantage of being flat, not 3D, as well as being a bit easier to sew than piping imo :)
These measurements will give a narrow 1/8" inset strip alongside a seam, however the measurements can be easily adjusted accordingly to make a narrow or wider inset as desired. If desired, you can even make the strips slightly different widths within the one garment to emphasise some seams over others or to give a better balance visually.
Select the side of the seam you wish for the inset strip to sit. For example, in this bodice I elected for the inset strip to be on the back side of the back/front side seam. This will be the piece the bias-cut strip will be pinned and stitched to first.
Note: IF you are sewing strips into multiple seams on the garment as I did for my dress in this example, then it is very important to be rigidly consistent throughout here. Because the inset strip is encroaching on the garment a little bit on one side of the seam the garment will look a little "off" if some strips are sewn to the front and some to the back. Pick a side and stick to it.
Cut the bias strips to be 1" width.
Voila!
