Charter bole
Indentations found in the boundary walls of Scottish buildings
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Charter boles are indentations found in the boundary walls of Scottish buildings constructed between the 15th and 17th centuries; they were used to denote ownership and responsibility for repair. They are similar to bee boles but smaller.
"in Scotland a single charter bole, one foot square or less, was often built into a wall to indicate its ownership".[1]
"charter bole: a rectangular recess used to house charter documents defining ownership of adjoining properties."[2]
It shows that the "wall belongs to the property on this side of it".[3]