Things You'll Need
Large sewing needle
Heavy nylon thread
Backpack straps are generally made of very strong materials, such as nylon, which make them durable. The material may still tear under strain, however, requiring you to either buy a new backpack or repair your current one. You can repair almost any strap with the right materials, and the process is not difficult for anyone with basic sewing experience. Choosing the proper durable materials is essential to making sure the backpack can withstand the weight of the items you carry in it.
Cut a piece of nylon webbing with the scissors that is long enough to stretch across the tear in the backpack strap and leave a few inches on either side of the tear.
Thread the needle with the heavy nylon thread and tie several knots at the end to ensure that it will be secure once sewn.
Push the needle through the nylon webbing and through the backpack strap. Push it back through near your first stitch. Continue working your way around, making a square with the stitches on one side of the tear, then filling the square with an "X" shape in the middle.
Tie off the thread and cut it with the scissors.
Thread the needle with more thread and do the same pattern on the other side of the tear. Create a square pattern, then fill it with an "X" shape in the middle.