What is that little hole at the bottom of a padlock for? This clever design feature prevents rust, lets water drain, allows lubrication when locks jam, and reveals how everyday objects often hide smart engineering details that make life safer and easier.

A padlock is one of those everyday objects we barely notice, quietly securing sheds, bikes, gates, and toolboxes. We twist a key, hear the click, and move on. But if you look closely at the bottom of a padlock, you’ll see a tiny hole—easy to miss, yet essential to the lock’s function.