Carbon cordage and tow is a carbonize polymer thread. The most commonly used source fibers are Rayon and PAN. These continuous fibers are made, then carbonized through a series of rollers, combined into bundles, and then collected into spools. The tow number 3k, 12K 24k, 36k, etc. tells you how many fibers per bundle. The tow can be used for many applications such as making pre-preg cloth, winding into complex shapes, and for making elaborate matrices.
In commercial heat treating, common uses are to hold felt insulation in place in small lab furnaces, for wrapping parts to provide insulation on certain sections, for sewing grraphite felt insulation, to hold parts in place, and for quick repair applications where bailing wire won't work! We keep a good inventory on hand for these uses.