Roughly hemispherical in shape, it measures about 0.6 metres across and 0.45 metres deep, with a hollowed upper surface that narrows to a point at the inner base. That hollow is the detail that matters. It is precisely the kind of form that, once you know what you are looking at, changes how the whole object reads.

Local tradition, recorded by Ua Broin in 1943, holds that this stone once served as a holy water font connected to a nearby church. A holy water font, for those unfamiliar with the term in this context, is a vessel used to hold blessed water at the entrance to a sacred space, typically allowing worshippers to bless themselves on entering or leaving. Stone fonts of this kind were often simple and robust, made to last even if the church they served did not. The field in which it now sits has its own suggestive name, the "trough field", which may preserve a folk memory of the stone's original function, or at least of its distinctive shape. The church it once belonged to has not been identified in the available record, but the survival of the font itself, and of the name of the field, suggests the association was remembered locally for a considerable time.

The stone sits beside a fence in the trough field in Rathcoole, to the south-west of Dublin. Rathcoole is a small town off the N7, straightforward enough to reach by road. The field itself is on private land, so anyone wishing to visit would need to make local enquiries before approaching. The font is not a dramatic or ornate object, and it rewards a certain patience; the hollowed surface and the way the granite has been worked are easier to appreciate up close, and the setting, unremarkable farmland with no obvious ecclesiastical trace remaining, gives the stone a slightly incongruous quality that is part of what makes it worth seeking out.