I found that this double-layered hemming method is commonly used abroad, and the original single-layered hemming is almost never seen.
Double-layer hemming, one side is completely sewn by machine, and the other side is finished by hand sewing.
Hemming effect.
Cut the length of the edge strip according to the work, the width is 21/2".
Spliced ??edge strips, facing each other, placed at a 90-degree angle.
Sew and press the line at the arrow, and cut off the excess fabric.
Iron the seams.