There are at least seventy-five of them, each measuring roughly nine metres by six metres, arranged at irregular intervals on both the northern and southern sides of the lake. They are the physical remains of charcoal production, an industry that once shaped this valley far more profoundly than its current identity as a monastic landscape might suggest.

Charcoal-making platforms, sometimes called hearths or pitsteads, were created by levelling a patch of ground on which timber could be carefully stacked, covered with turf or earth to restrict airflow, and slowly burned to drive off moisture and gases, leaving behind the dense carbon fuel that iron smelting and smithing required. The platforms at Lugduff were recorded by Ua Riain in 1940 and again noted by Healy in 1972, the latter accounting for around forty of the oval features. Their presence in such numbers around Glendalough points to an organised and sustained industry rather than occasional, opportunistic burning. The valley's oak woodland provided the raw material, and the proximity to Reefert Church, a Romanesque site associated with the kings of Leinster, raises questions about who controlled and benefited from that production, though the sources do not settle that question.