You can use something to open both sides of the zipper head a little. Just put the zipper on one side in first, and then put the zipper on the other side in. After the two zippers are put in, you can use needle-nose pliers to tighten it a little. In this way, the zipper will not fall out. Note that the quality of the zipper head must be better. If it is bad, it will break if you touch it. It must be the same size as the zipper. If it is too small, it cannot be pulled, and if it is too big, it cannot be locked. When I was in junior high school, I always broke zippers. I just took off the zippers from many old clothes at home and put them on.