A cairn, in the broadest sense, is a mound of stones heaped over a burial or used as a landscape marker, and the pair at Glencap Commons were once substantial enough to leave a clear impression: the larger of the two measured roughly sixteen metres across and stood some two and a half metres high, with its smaller companion, about nine and a half metres in diameter, positioned approximately twenty-five metres to the north.

The earliest documentary record of these monuments appears in the Ordnance Survey letters, a remarkable nineteenth-century archive in which scholars and local informants wrote detailed accounts of antiquities, placenames, and topography as the first systematic mapping of Ireland was being carried out. The Glencap Commons cairns are noted in the volume compiled by O'Flanagan, published in 1928, which drew on fieldwork and correspondence from that earlier surveying era. By the time the cairns were formally assessed for the Archaeological Inventory of County Wicklow in 1997, they had effectively vanished from the surface, leaving only their recorded dimensions and the slight contours of the slope as evidence that something once stood here.