Horseshoes have long been considered lucky. They were originally made of iron, a material that was believed to ward off evil spirits, and traditionally were held in place with seven nails, seven being the luckiest number. The superstition acquired a further Christian twist due to a legend surrounding the tenth-century saint Dunstan, who worked as a blacksmith before becoming Archbishop of Canterbury. The legend recounts that, one day, the Devil walked into Dunstan’s shop and asked him to shoe his horse. Dunstan pretended not to recognize him, and agreed to the request; but rather than nailing the shoe to the horse’s hoof, he nailed it to the Devil’s own foot, causing him great pain. Dunstan eventually agreed to remove the shoe, but only after extracting a promise that the Devil would never enter a household with a horseshoe nailed to the door.
According to Wikipedia:
Horseshoes have long been considered lucky. They were originally made of iron, a material that was believed to ward off evil spirits, and traditionally were held in place with seven nails, seven being the luckiest number. The superstition acquired a further Christian twist due to a legend surrounding the tenth-century saint Dunstan, who worked as a blacksmith before becoming Archbishop of Canterbury. The legend recounts that, one day, the Devil walked into Dunstan’s shop and asked him to shoe his horse. Dunstan pretended not to recognize him, and agreed to the request; but rather than nailing the shoe to the horse’s hoof, he nailed it to the Devil’s own foot, causing him great pain. Dunstan eventually agreed to remove the shoe, but only after extracting a promise that the Devil would never enter a household with a horseshoe nailed to the door.