Denim, although known for its durability in work and play, commonly wears out at high stress points like the center seam, knee, hem and inner thigh. Depending on the wearer's habits, other areas can also become threadbare, eventually progressing into unacceptable holes or tears. Keeping a wallet or cell phone in a back pocket every day, for instance, is a good way to strain the lower pocket seam. Repair these unsightly back pocket holes and prevent further deterioration of the fibers with a basic zigzag stitch.
Perform the repair on the worn-out fabric before the horizontal threads, which make up half of the denim's weave, break. The blue vertical threads are typically the first to break, leaving white horizontal threads behind. Once those also break, a full hole is created and the final repair job becomes both less stable and more noticeable.
Clip the loose, frayed thread ends to create a clean working space around the damage.
Cut a piece of matching denim that is 1/2 inch bigger than the hole, only if the hole is large and spreads easily with tugging. Slide the piece inside the jeans to cover the hole from the inside, and pin it around the hole.
Slide the damaged back pocket area beneath a sewing machine's presser foot. Arrange the fabric so that only one layer is between the presser foot and the feed dogs. Slide the presser foot over the back pocket, and insert the needle just below the pocket.
Zigzag stitch up and down over the damaged area, as close to the pocket as possible. Go over the area several times for full coverage.
Raise the presser foot and pull out the jeans. Clip the thread ends and trim the edges of the denim patch to 1/4 inch.
To get the needle closer to the pocket, push a folded piece of denim under the back side of the presser foot to raise it slightly. Carefully stitch the hole as close to the pocket as possible. The smaller the hole, the easier the repair. Turn jeans inside-out regularly to catch early damage, which appears as fuzzy, pilling sections of fabric.