Why does the zipper snag on the garment lining?

Q: Why does the zipper snag on the garment lining? Snagging is a garment construction issue in most cases: the lining, a seam or a loose thread is being caught by the slider or teeth. Finding the exact point of snag before trimming anything keeps the evidence intact and avoids a fix that creates a new fault. Open and close the zipper slowly and find the exact point of snag. Look inside for lining fabric, interlining or a raw seam edge near the chain. Check for a loose thread or a seam allowance that crosses the teeth. Examine the slider for a burr or a rough edge that catches fabric. Fit a slider with a smoother profile or adjust the seam allowance on a scrap. Snagging that disappears when the lining is held away is a construction issue. Snagging on a bare chain with no fabric nearby points to a rough slider and should be checked against a good sample. Trimming the lining is a quick test, but the seam allowance needs a permanent fix before production.