That is an interesting foot! i'm wondering if the decorative material you are couching goes under that little clip. If it is a little clip... :-0
here's a definition of "Couching"
Couching is derived from the French word couchier and is the art of embroidering by laying threads flat on a surface and sewing them down by stitches sewn at regular intervals.
In centuries past, couching was a very popular form of decoration for the upper-class clothing of the time. People of means would often wear items which were covered in couched and embroidered designs.
The couching of today is generally done by laying a length of yarn, cord, or ribbon down on a piece of fabric, and then sewing it in place with a zigzag or other decorative stitch. Today, couching is used to sew on many of the more decorative fibers and trims available to those who sew at their local craft stores.