These are bullauns, stones bearing one or more shallow basins that are found across early medieval ecclesiastical sites in Ireland. Their precise original purpose remains debated; theories range from liturgical use to the grinding of pigments or grain, though many became associated with folk curing traditions long after the monasteries that surrounded them had fallen into ruin. What makes the cluster at Sevenchurches, as this part of Glendalough's monastic landscape is sometimes called, quietly unusual is their distribution: two of the four lie directly in the river itself.

Healy, writing in 1972, recorded one of the stones in some detail. It is a substantial granite boulder measuring roughly 1.1 metres by 1 metre and standing about 0.4 metres high, positioned beside the river to the west of a mill. Its single basin is around 0.3 metres across and 0.15 metres deep, with a conical rather than flat-bottomed section, which is a relatively distinctive feature among bullauns. A second stone lies just 3.3 metres to the east, and two further examples have been recorded within the river channel itself. Granite, the local bedrock of the Wicklow Mountains, was the material of necessity here, and its durability has kept these stones legible across many centuries. The presence of four bullauns in such close proximity, one reportedly outside a caretaker's house, suggests they were gathered or at least recognised as a group at some point, though how long they have occupied their current positions is not recorded.