Each measures roughly nine metres by six, just large enough to have once held a carefully stacked mound of timber covered with earth or turf and left to smoulder slowly over days. These are the traces of charcoal production, an industry that leaves behind almost nothing except the levelled, scorched ground on which the burning took place.

Charcoal-making platforms of this kind, sometimes called hearths or pitsteads, were created by clearing and flattening a patch of hillside just enough to hold a timber pile steady during the slow, oxygen-starved burn that converts wood into charcoal. The resulting fuel was essential for smelting and metalworking, and woodland areas near reliable water sources were often worked intensively for this purpose. At Lugduff, the platforms were recorded in two groups: Ua Riain noted around 75 of them in 1940, arranged on the northern and southern sides of the Upper Lake, while Healy's later account from 1972 documented a further 40 similar features in the same general area. Taken together, this represents an unusually dense concentration of industrial activity tucked into one of the most visited monastic landscapes in Ireland, where the focus tends to fall almost entirely on the ecclesiastical remains nearby.