Zippers are designed for trouser legs. First, it is for decoration. Second, when you wear different boots, you can unzip them according to the height of the boots' uppers, so as to increase the width of trouser legs and improve the wearing comfort. Third, when you put on and take off your pants, your feet are not easy to get in and out. At this time, the zipper is unzipped, and the feet are easy to get in and out.