The invention of the safety pin is a story of caution. In order to repay a $15 bet, Walter Hunt designed a fastening pin out of copper wire and a clasp to hold the end of the wire. His invention is the basis of the modern day safety pin, but Hunt sold his patent to WR Grace and Co. for $400, using the money to pay off his friend. As we know today, the safety pin is an invention that is used throughout the world, and one that made WR Grace Co. millions of dollars. Mr. Hunt only made $485.