Industrial sewing machines are used in mass garment production and come in different types for specific tasks. Single needle lock stitch machines are the most widely used and can join multiple fabric layers together for light to heavy materials. Overlock sewing machines have 3 to 5 threads and make edge stitches for finishing knit garment panels and seams. Flat lock sewing machines come with 2-3 needles and make cover stitches for hemming knit sleeves and bottoms or decorative seams. Feed off the arm machines make chain stitches for flat seams like shirt sides and jean inseams.