Waxed LINEN lacing (cord, twine, thread), 3 ply, 25yd rolls: available in black or natural.
The roll looks big in the photo, but it's about 1.75" x .5", 1mm thickness.
Used in rugmaking to sew the braids into a rug, or for quilting, jewelry making, upholstery or other crafts. The wax makes the lacing slide through the fabric easier. Linen is much more durable than cotton. It'll last a lot longer so your rug or quilt won't soon come apart.