Since at least the Middle Ages people have used horseshoes as protective talismans and good-luck amulets. They were originally made from iron, which was considered a magical substance in prehistoric times because it was stronger than other materials and was able to withstand fire. Another aspect of the horseshoe that added to it’s good luck was the fact that it was commonly held in place by seven iron nails. Since ancient times, the number seven was considered very important.
Finding a horseshoe is very lucky if the open space is facing toward you.