Have you ever gone about your normal life, interacting with random people, but totally oblivious to the fact your fly's been undone the entire time? If it's due to your zipper not "zipping", and not gross negligence, then this is the tip for you!
Using just a key ring, you can prevent your zipping from unzipping, and also being known as the person always "letting the breeze in".
With this tip, a key ring works best. A key ring is used to typically keep your keys together, but it just also happens to be a great solution to preventing your zipper from falling down.
You can buy one from Amazon, but most people should already have one.
Loop the key ring through the top of the zipper's head and make sure it's "clicked" into place by rotating it 360 degrees while fastening through the hole.
This is where the magic happens. Zip your zipper all the way up and attach the key ring around the button.
Finally, you can button your pants (or shorts) and say goodbye to all of the ignorant flashing you've been doing.