Cairns, in this context, are mounds of heaped stone raised over burials or as territorial markers during the Bronze Age or earlier; these examples are circular in plan and, while modest in scale, are old enough to have been absorbed into the practical geometry of modern surveying. The largest of the three occupies the highest point of the hill at 554 feet above sea level and was at some stage pressed into service as a trigonometrical point, the kind of fixed reference used by Ordnance Survey teams to map the landscape. That a prehistoric monument should double as a surveying station is less surprising than it sounds: prominent hilltop cairns were often the most logical place to plant a trig marker, their elevation doing the same work for ancient builders as for modern cartographers.

The three cairns are clustered within a tight radius. The largest measures twelve metres in diameter, while a second cairn, roughly nine metres across and still standing about 1.6 metres high, lies approximately twelve metres to its south and now bears a modern concrete trigonometrical station on its crest. A third and smaller cairn, five metres in diameter and just half a metre high, sits about fourteen metres to the north-east of the largest. All three have been denuded over time, their profiles flattened by the removal of loose stone and further disturbed by the infrastructure installed around them. The relay equipment on the summit has compounded the damage, leaving the cairns in a stripped-down state that makes their original form difficult to read from the ground.