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.

Some features exist for hygiene. Brass doorknobs and pulls are still common because brass is naturally antimicrobial, killing bacteria on contact.

Even cars hide clever cues—like the tiny arrow on the fuel gauge that quietly tells drivers which side the gas tank is on. Small details, big impact.

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