In Ireland, England, Wales, and the Scandinavian Peninsula, horse skulls have been found concealed in the structures of buildings, usually under the foundation or floor. Horse skulls have also been found in buildings in the United States, although in far fewer numbers. As part of the larger folk tradition of concealing objects in structures, horse skulls are related to concealed shoes, dried cats, and witch bottles.
There are two main theories as to the reason for depositing the horse skulls in buildings: as a method for enhancing the acoustics of a room, such as in a church or in a threshing barn; or as a method for repelling evil spirits such as witches and ghosts.