Reinforcement and Decorative Stitching
Chances are that if you've ever seen a pair of blue jeans, you've seen a bartack. A bar tack stitch is basically a tight zigzag that is repeated back and forth over itself to reinforce a piece that is sewn together. It helps resist rips in the fabric and increase strength of the overall product. When made commercially, industrial machines usually have a bartack attachment or a machine designed specifically for bartacking is used. In the home, you can simply use a tight zigzag and run it back and forth several times to get the desired effect.
Any place on a garment that has stress points which would otherwise rip after a few uses would have a bartack stitch to reinforce those areas. You'll notice them on a pair of blue jeans around the pockets, belt loops, zipper fly and hips. They're also used heavily on military and emergency uniforms, protective equipment, bags, luggage, and sporting gear. With sporting equipment, bartacking is considered a safety measure and is part of the item's design. Buttonholes are another example of the bartack in use. Many buttonholes, particularly those made with home sewing machines, have one or two bartacks on one or both ends of the buttonhold for reinforcement. It also is a basic decorative stitch that can be used for embroidery purposes.
Whether you're using a bartack for reinforcement purposes, decorative items, or just wondered what that stitching was for on your clothes and gear, the bartack stitch is a flexible basic way of securing fabric in a functional way and giving items their unique stitched look.