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A horizontal bar above a broad arrow, cut into stone as a height reference.
Also known as: Cut benchmark, OS benchmark, Crow's foot mark
An Ordnance Survey benchmark is a horizontal bar cut into masonry above a broad arrow pointing up at it. The bar is the reference: a levelling staff was rested on it and its height above the national datum recorded, so the mark is a fixed point in a height network rather than a boundary mark or a claim of ownership. Tens of thousands survive on walls, bridges and church plinths, and most are no longer maintained — the network having been superseded by satellite positioning.
Marks a fixed height reference rather than a boundary or an owner: the horizontal bar is where a levelling staff was rested, and its height above the national datum was published.
United Kingdom · Contexts: History, Navigation
Survives in tens of thousands on walls, bridges and plinths, and is largely no longer maintained: the levelling network it belonged to has been superseded by satellite positioning, so a benchmark found today is a historical artefact with a published value.
Nineteenth century to the late twentieth · Contexts: History
A short horizontal bar cut into stone with a three-pronged arrow beneath it, its point touching the underside of the bar.
Both are three-pronged arrows cut into British stonework.