Why does my zipper skip teeth when closing?

Q: Why does my zipper skip teeth when closing? Skipping means the slider passes a tooth without meshing it. It can start from a single bent tooth, a worn slider, or a chain that is not the size the slider expects, and the pattern along the tape usually shows which. Mark the first point of skip with chalk and open the zipper to inspect there. Look for one bent or rolled tooth that the slider cannot pick up. Measure the slider gap; wear opens the gap gradually and skipping is an early symptom. Check that the slider and chain are the same size and type, especially after a replacement. Run the zipper slowly and feel for a step or catch that indicates a high tooth. A single bent tooth can often be traced to handling before sewing, while regular skipping along the length points to slider wear. Short runs of twenty to thirty cycles on a sample will show whether the fault is progressive. Report the position and the cycle count so the maker can judge the cause.