“One of the Stenness stones was particularly noteworthy. This was the Stone of Odin, a six-metre high, one-metre wide and forty centimetre thick monolith destroyed in 1814, through which there was a hole. Through this hole, lovers would clasp their hands and enter into marriage. (This is a variant on the time-honoured custom of handfasting, a form of marriage by public declaration. Couples who wished to divorce could do so by leaving through seperate doors of a church after the service.)”
From “Scotland:Myth, Legend and Folklore” by Stuart McHardy 1999, pages 107-108.