It's this blade that rides against a seam line, or fabric edge, that creates straight and even lines of stitching. ... It is particularly good when joining two edges of fabric together, known as edge joining. It is also great foot to use to do topstitching and understitching.
Very quick and efficient service.
I have used the foot a lot as I have been making masks. Finished effect good but think parts of the foot seem flimsy. Not the main body but the edger.