* The Greeks always believed that iron would ward off evil.
* Also, the Greeks believed that the crescent moon was good luck because it brought fertility.
* The two combined would make a really good source of good luck
* Another reason: St. Dunstan was a blacksmith
* One day the devil entered his store asking for shoes for his horse
* Seeing that it was the devil, St. Dunstan tricked the devil and chained him to the wall
* St. Dunstan let the devil go as long as he promised that he would never do harm to any house that had an upside down horseshoe.