Mystery solved!

The popular item of clothing can be found hanging in most people's wardrobes, but the design adopted so many years ago is not one we question too often.

In particular, Levi’s jeans have a series of metal studs that are not purely there for decoration.

They're a historic part of the design, dating all the way back to 1873 when it was patented, so a long-lasting inclusion on our pairs of jeans.

Recently, someone on Reddit asked about the stud’s function. The wrote: “Do they serve a purpose, practical or otherwise? If not, why are they there?”

The answer is actually to do with the time period when they were created.

Back in the day people were wearing jeans to do physically demanding jobs such as working in the mines.

The small circular studs called rivets were added in order to prevent the pockets from fraying.

Pockets can be affected due to it being where the stitches connect and potentially rip. Heavy objects placed in the pockets can also stretch or put pressure on the fabric.

Reddit users were quick to answer the original poster, sharing the history of the design.

One person commented: "They're rivets. Levi's made them popular. The rivets were implemented to make jeans more durable at the seems versus traditional sewing techniques."

Another said: "Observe the location of the rivet on the garment. It is positioned near where the pocket starts so that it may serve as a structural reinforcement component in order to prevent the pocket from being torn off of the garment."

Levi’s official website said of the design: “By adding metal rivets to work pants, which would be known as blue jeans, they created stronger pants for working men.”

Another detail people have often questioned is the smaller pocket inside the larger pocket.

Back in the day it would be common to carry around a pocket watch (before wristwatches were even a thing), and so it made sense for Levi's jeans to have a tiny pocket inside the larger jean pocket for the pocket watch.