According to Carnivale Tattoo, horseshoe tattoos symbolize good luck and protection. When a horseshoe is etched onto the skin and the ends are facing up, the horseshoe acts as a cup that catches good luck. When the ends are facing down, this symbolizes bad luck emptying out of the cup.
In early times, horseshoes were held in place with seven nails, due to the fact that seven was considered a lucky number. Today, it is common for horseshoe tattoos, amulets and charms to contain seven holes. During the middle ages, a common belief was that witches were afraid of horses and horseshoes because the shoes were made from iron, which was believed to ward off evil spirits because it could withstand fire. It was believed if a homeowner nailed a horseshoe above the door, witches would not enter the home.