Bar tacking is a specialized sewing stitch designed to provide immense tensile strength to the garment or equipment it is used on. Bar tacking is commonly used on backpacks, tents, tactical gear, and other heavy wear sewn items where normally sewn stitches might give way at a crucial moment. In general, bar tacking is a sign of good quality, although the rest of the product should always be looked over carefully as well. When a sewing pattern calls for bar tacking, it indicates that the designer feels that section of the pattern is a critical area that needs extra reinforcement.

Bar tacking is accomplished by sewing a very tight zigzag stitch across the width of the material. In some cases, the manufacturer may go over the bar tacking again, causing the stitch to have an x-like form. Usually, very strong threads are chosen for bar tacking so that they will stand up to high pressure. When done correctly, bar tacking can help support loads of up to 400 pounds (almost 200 kilograms). Many backpacking companies in particular pride themselves on the number of bar tacks integrated into their products, claiming that they will wear harder and longer than the competition.

For commercial work, specialized bar tacking sewing machines are capable of handling high volumes of bar tacking through heavy materials like nylon webbing and canvas. Commercial bar tacking machines tend to be expensive, however, and smaller companies prefer to modify their existing sewing equipment. Home sewers can bar tack if they have a zigzag setting on their sewing machines, although they may have to do it by hand if the material is very thick. In both cases, a heavy weight waxed thread should be used.

Bar tacking works to reinforce material by spreading pressure more evenly along the width of the fabric, with a large number of stitches covering a small area. When pressure is put on the bar tacked area, the thread will not give way as readily, because it is not in a straight line in grain with the fabric, as most sewing is. Indeed, fabric will more frequently give way around bar tacking, especially if it is old, or if it has been stressed by the elements.

Bar tacking can be seen reinforcing rock climbing harnesses, hang gliding gear, and a wide variety of other products manufactured for outdoor sports. Because much of the gear bar tacking is used on is critical to survival, it is important to frequently inspect and test such gear and to discard equipment that seems unreliable. In general, if support gear is frayed or worn, stretched out of shape, or torn, it is probably not safe for use.