Usually to sew on the inside of skirts, shorts, trousers, and jackets, instead of using a zipper or buttons to securely close the waistline of bottoms or the tops of skirts and jackets. When sewed on the garment the catch snaps shut to close and snaps open to take the garment off. Hope this helps. If you double click on the photos you should be able to view a bigger and better picture. You can also go onto Google and type the title in the search bar to find out more about this type of sewing item. Thanks for the question.