The principle behind them is straightforward: stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil, with the cracked and shattered remains of those stones accumulating into a characteristic horseshoe-shaped mound over time. What makes the Lisdangan cluster quietly remarkable is both the concentration of sites, three mounds in close proximity and a fourth just ten metres or so to the south-east, and the survival of a piece of physical evidence that rarely endures.

All the mounds have since been levelled, their material spread into a single broad deposit of burnt stone across the pasture. A 1937 Ordnance Survey map recorded at least two of the adjacent mounds before they were lost to that process. What persists in the record, however, is more tangible than topography. Bowman, writing in 1934, documented a wooden trough found close by, a rare survival given how seldom organic material makes it through the centuries. The description is precise: the planks at the base varied from two and a half to three and a half inches in thickness, smooth on the upper face and rough-hewn on the underside. That distinction between the worked surface and the raw one suggests careful but practical construction, the kind of detail that shifts a prehistoric technology from the abstract to the immediate. The site lies around twenty metres east of a stream, which fits the usual pattern; a reliable water source was essential to the whole operation.