Check for fabric, thread, or debris caught in the zipper
Gently pull the zipper back and forth to free it
Use a pencil graphite, zipper wax, or soap on the teeth
Align both sides of the zipper before pulling
Tighten a loose zipper slider with pliers
Replace a broken zipper pull with a key ring or paper clip
Sew or trim any snagging fabric near the zipper path
Replace the zipper slider if it is worn out
Replace the entire zipper if the teeth are damaged
Take the backpack to a repair shop if the zipper cannot be fixed