Designed for adjustable straps. 
Many backpacks come with molle like straps on the backstraps but are missing the chest strap.

With this you can easily add a chest strap without the hassle of removing previous straps or sewing. Just put the strap in this clasp and the hook it to horizontal straps on your backpack!

Easy-peasy-lemon-squezy!

(I've never written the word strap this many times in such short text before in my life. I am sorry!)