Corner dust guards. They make it easier to sweep dust out of the corners. : r/thisisthatthing
Winchester Mystery House - These beautiful intricate "dust corners" are installed on the majority of staircases in Sarah's home! Made popular during Victorian times - this small feature made sweeping the stairs
Dust Corners Plated Brass, Satin Nickel Dust Corners Set of 12
Decorative Brass Dust Corner With Choice of Finish | Elegant home decor, Antique hardware, Elegant homes
Stamped Tin Stair Dust Corners | Hippo Hardware & Trading Company
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