|You may have seen this written up in Threads or elsewhere. It is a way to get a narrow machine stitched hem; particularly useful in adding weight to lightweight fabrics or for using on a bias skirt.
1. At the machine, fold your raw edge over to the wrong side about 1/4"-3/16" and sew 1/8" from the edge. You don't need pins for this, just foldover as you sew, maybe 3" or so at a time.
2. Using very sharp scissors (duckbilled applique scissors are a good choice) trim fabric very close to the stitching.
3. Now foldover again to the wrong side, and stitch on top of the original stitching.
4. Press hem.
You can, if you want a bit more weight, make a first line of stitching 1/4" from the raw edge so you have a built in guide for folding over your fabric.