Overlock sewing machines will trim, stitch and overcast seams as they sew, and they sew faster than conventional sewing machines, up to 1,500 stitches per minute. Because of these features, an overlock can save time and give a professional appearance to items constructed. The overlock machine can be used to sew a wide variety of items-from placemats and napkins to sportswear and draperies. Sewing items, such as a T-shirt or jogging outfit, can be done in minutes and the seams of the finished products will look like those in ready-to-wear. The overlock can also be used to finish the edges of seams, which will be sewn with a conventional machine. Decorative effects can be achieved by using special threads in the loopers. Threads, such as metallics, silks and perle cotton, can be used to sew seams or to finish garment edges. For special effects, fine knitting yarn, buttonhole twist, crochet thread and even narrow ribbon can be used. Overlock sewing machines are specialized, but they do not replace the conventional sewing machine. Overlocks form interlocking stitches using one or two needles and one or two loopers. The overlock stitch is more like crochet or knitting than the stitch of a conventional machine. Loopers replace the traditional bobbin and interlock threads together.