The 'Gem' paper clip, the most common double-oval design we use today, was never actually patented, but it appeared in the late 19th century as a solution to organizing documents without piercing them. Before the paper clip, papers were held together by pins, string, or ribbons, which damaged the paper. The Gem clip used the principle of elasticity; the wire is bent into a shape that exerts enough pressure to hold a few sheets of paper but can be easily removed. Interestingly, during WWII, the paper clip became a symbol of Norwegian resistance against Nazi occupation. Norwegians wore them on their lapels to represent unity (being 'bound together') and loyalty to their king. It is a masterpiece of 'economical design'—an object that is perfectly functional, cheap to produce, and impossible to improve upon.