A questioner said:
What are these medal things on the corner of these stairs and what is their purpose?

More info:
These small triangle pieces of decorative looking medal are on the corner of every step of this antique staircase. They are maybe an inch or so from top to bottom.

Some of the answers:

Corner dust guards. They make it easier to sweep dust out of the corners.
I’m aware I spelled medal instead of metal. Spelling is a known weekness of mine.
Stair dust corner. You can find it it Amazon if you search using these words.
wow, never seen these before.. definitely getting some for my victorian staircase !
I was all excited to comment. Ooh ooh I know this one!
Where’d you find them? The only place I’ve seen them is in the Winchester House in San Jose.
I want these for every corner in my home
Damn that’s a smart idea!
Low key or maybe high key I thought these were some futuristic stair cameras I think
“Metal”They’re designed to keep the stair corners clean since dirt can accumulate in the corners and be hard to get out. Clever idea, actually.
It keeps the dust out of the corner as other people have mentioned, but it may also be covering wood that wasn’t cut exactly right so they’re covering up small gaps.
My first thought was “I don’t what that is, but that sure would make cleaning easiest”
Old Victorian houses sometimes have them. Corner dust guards fell out of favor with the invention of the vacuum cleaner. Sweeping dust out of a corner is hard, vacuuming it is easy.
Idk but if I had them I’d be glad not to have to sweep those corners.
These were (if I remember correctly) invented by Sarah Winchester and can be found in the Winchester Mystery House in California.