I’ve always kept a collection of padlocks for securing my belongings at the gym, on my locker, and even in public bathhouses. They’ve always been reliable, but I started noticing something unusual: a small hole near the keyhole of each lock. I didn’t think much of it until my curious daughter asked, “What’s that hole for?”.

Her question sparked my curiosity, and I decided to look into it. I discovered that this seemingly insignificant hole actually serves an important purpose. Many people use padlocks without realizing the subtle design features that make them effective and long-lasting. That tiny hole is part of a clever drainage system. When water seeps into the lock—whether from rain or humidity—the hole allows it to escape, preventing rust and corrosion that could damage the lock. Without it, the lock could become stiff or stuck, leaving you locked out.