Each one measures roughly nine metres by six, just large enough to have held a carefully constructed mound of timber and turf. They are the physical traces of charcoal production, an industrial process that once shaped these quiet Wicklow valleys far more profoundly than their present atmosphere suggests.

Charcoal-making platforms, sometimes called hearths or pitsteads, were created by levelling a section of hillside to provide a stable base for the charcoal burn. Coppiced wood was stacked in a carefully managed pile, covered with bracken, earth, or turf to restrict airflow, and then slowly smouldered over several days. The result was a lightweight, high-carbon fuel essential for smelting and metalworking. At Glendalough, researchers recorded at least seventy-five of these platforms on the northern and southern sides of the Upper Lake alone, with a further forty of similar form noted in later survey work. The sites were recorded by Ua Riain in 1940 and subsequently by Healy in 1972, suggesting a sustained interest in what amounts to one of the more concentrated industrial landscapes surviving in the Wicklow uplands. The precise period of activity is not recorded in the available evidence, though the scale points to organised, repeated use of the woodland over a considerable time.

The platforms are most legible on the ground when leaf cover is low, when the slight terracing of each oval becomes visible against the slope. Reefert Church, a small Romanesque ruin within the monastic enclosure, provides a useful landmark for the south-western cluster. Visitors who move beyond the main monastic path and into the surrounding woodland are likely to find themselves stepping across these subtle earthworks without quite realising what they are.