The Cheviots abound with long earthen banks, sometimes containing stone or rock. Some of these are boundary dykes, marking the edges of ancient estates; some may be the result of medieval emparking that typically enclosed an area of land for hunting. Others are just field boundaries or dykes protecting cultivation. Then there are structures called cross dykes.
The archetypal cross dyke consist of a bank and an accompanying ditch built across a ridge, usually at right angles to it. Usually the bank peters out on either side of the ridge when the slope becomes steep. Some cross dykes are up to four feet high in places, ten feet wide and up to 300 yards long. Erosion, stock, forestry and farming have damaged some of them and destroyed others.
No-one knows what they were for. It’s been suggested that they marked boundaries, protected nearby settlements from stray cattle, acted as control posts for passing travellers or discouraged reivers. Those few that have been examined in detail turn out to be pre-Roman in origin, but that doesn’t mean they all are. Nor should we accept that they were all built with a single purpose; things are rarely that simple.