Have you ever walked by a home and noticed the window bars puffing out slightly, almost like a curved belly pressing outward from the glass? They’re not just a quirky design choice or a playful architectural twist — those bulging bars, often called “potbellied” window bars, actually serve a fascinating and functional purpose.

For centuries, window bars have been a practical way to deter intruders, keeping homes safer while allowing residents to leave windows open for fresh air. Security, after all, was the original reason for their invention. But somewhere along the way, form met function — and the potbelly was born.

So, why the outward curve?