A bar tack is a special stitch used to give massive strength to high-stress areas. (These stitches are used on rockclimbing slings, a testament to their strength.) Bar tacks are used as reinforcement in key areas on One Planet rucksacks: in fact, the Exact Fit harness uses roughly 50 of these. Our bar tacks consist of 42 or 28 individual stitches, depending on the application, done on a special machine.