Hello! I bought a box of attachments, and there was a back-mounted adjustable hemmer in it. I have no machines that use this type of foot. If anyone is interested and can use this, contact me through email@example.com . I had no idea what used these until a search, and very old Singer 66-1s use them. I have the side mounted 66s and some rotary machines. Thank you! Carol V. from Pa.