its called a rivet
Rivets
In 1871, Latvian immigrant Jacob Davis pioneered rivets while working as a tailor in Reno, Nev. Davis had originally used rivets on horse blankets, and he found they worked well for re-enforcing the stress point in men’s work trousers—particularly the corners of the back pockets and the crotch, which often tore apart when exposed to heavy duty wear and tear.
Since Davis did not have the money required to patent the technique of using rivets, he reached out to Levi Strauss to see if he was interested in applying with him. In 1873, the pair received a patent for “improvement in fastening pocket-openings.” This was the birth of what we now know as the blue jean. Today, rivets continue to strengthen and reinforce the most vulnerable parts of our jeans.
It’s worth noting that Levi Strauss & Co. was the first company to make riveted pants, creating a new category of workwear.