Many people think it’s just decoration!
This creates a ventilation gap. The outwardly curved strip doesn’t adhere evenly to the glass, allowing air to circulate and accelerating the sill’s drying time.
This simple innovation protected wooden window frames for centuries before modern seals were invented.
Historical Response: Protection from Intruders
In older buildings, especially in Europe, window grilles were designed with curved bottom edges to prevent intruders from using ropes or hooks to climb inside.
Think about it: straight, horizontal poles are essentially a ready-made ladder. A thief could wrap rope around them or use a grappling hook to climb. But curved poles, especially those that curve outward, make this much more difficult. The curve disrupts the straight line, making it difficult to grab onto or gain a foothold.
