At Koala-Gear, we are really proud of our MoonLock mechanism, which is patent-pending.
The MoonLock closes geometrically, meaning the two flaps close securely on top of each other. This creates a strong seal (stronger than a magnet), and serves the additional function of keeping water out of your bag.
Inherent in the way the MoonLock system works is that if the bottom flap is opened while you are wearing LIO, you will feel the flap on the back of your neck. If someone tries to access your belongings inside LIO while you are wearing it, you will know.