The paper clip seems to be the simplest of all inventions. It is nothing more than a small piece of bent wire with paper sandwiched between it. But the paperclip went through many design iterations before it came into the shape we use today. In the past people used to use pins to hold their pages together. But needles damage paper and can injure users by pricking their fingers.
A Norwegian inventor named John Waller filed a patent application for a wire paper clip in 1901. However, all of these early paper clips had some problems. When the clamp is pushed, the protruding wire ends dig into the paper and puncture it, causing even more damage to the paper than the needle. Later, in 1899, engineer William Middlebrook of Waterburg, Connecticut, USA invented a machine that bent wire paper clips. Because the paper clips made by his machine had a double loop, they were very similar to the paper clips we use today.