Stair dust corners introduced at the end of the 19th century to make sweeping easier. They keep dust from accumulating in the corners : r/Damnthatsinteresting
Dust Corner for Stair Steps Polished Brass Decorative Star Design - Etsy
Brass Staircase Dust Corners | Van Dyke's Restorers
20PCS Corner Dust Guard for Steps, Dust Proof Guard, Stair Corner Dust Guard, Dust Corner Protector for Furniture and for Home Wall Edges - Etsy