The hem may be sewn down with a line of invisible stitches or blind stitch, or sewn down by a sewing machine. The term "hem" is also extended to other cloth treatments that prevent unraveling. Hems can be serged (see serger), hand rolled and then sewn down with tiny stitches (still seen as a high-class finish to handkerchiefs), pinked with pinking shears, piped, covered with binding (this is known as a Hong Kong finish), or made with many other inventive treatments.