Schmetz Hemstitch Needles are for producing hemstitch effects, a decorative openwork stitching, on tightly woven fabrics. They are also called wing needles. They are only for zigzag machines with transversal hook. Twin Size 100 1 pc- One wing needle and one regular needle on a crossbar from a single shaft. Use two spools of thread and pass each thread on a different side of the tension discs and thread one thread one into each needle. Only one bobbin thread is used and the stitches create a double web of stitches on the back. Must use with a zigzag stitch plate.