 The purpose and meaning of the stones are only partially understood, although some think that they served as personal memorials, the symbols indicating membership of clans, lineages, or kindreds and depict ancient ceremonies and rituals Examples include the Eassie Stone and the Hilton of Cadboll Stone.It is possible that they had subsidiary uses, such as marking tribal or lineage territories.It has also been suggested that the symbols could have been some kind of pictographic system of writing.