Q: What is the difference between closed-end and open-end zippers?
A closed-end zipper has a single slider and a permanent bottom stop, so the two halves never separate. It is used where the opening only needs to part from the top, such as trouser flies, skirt openings, pockets and many bags.
An open-end, or separating, zipper carries a pin and a retainer box at the bottom. The slider threads the pin into the box to engage the chain and releases it when pulled fully down, which lets a jacket open completely. The box and pin add roughly 10 to 15 mm to the assembly and must be sewn so the box sits below the seam line.
A third type, the two-way or double-slider zipper, has sliders at both ends of a closed or open chain, allowing opening from either direction; it is common on parkas, luggage and tents. Specify which type you need at inquiry stage, because the bottom tooling, the pattern allowance and the slider count all change. Mixing a closed-end body pattern with an open-end zipper is a frequent and expensive sampling error.