**In-built lock. Its already there on your zip. Just check it.**

Most of the jeans zips now come with **In-built lock**. When you zip just make sure that zip-hooker is placed vertically Down (this will lock the zip.) Just try to open the zip with hook placed down. It won't open Just like below image.(Zip hook placed vertically down here.)

![enter image description here][1]

If you zip and don't keep hooker down zip will eventually run down due to strain on it.

Visit [YKK website][2] for more info. If you see zips anywhere, there's 70% chance that it's made by YKK.

Some low quality jeans might not use YKK produced Zip. That's why you should always check YKK mark on zip before buying jeans.


  [1]: https://i.sstatic.net/W89Uj.jpg
  [2]: http://www.ykkfastening.com/products/types/s_zipper.html