It is modest in scale, roughly nine metres long and seven metres wide, defined on two sides by field walls and on the other two by a natural scarp in the land. Inside, numerous set stones mark where children were laid to rest. This is a cillín, the Irish term for an unofficial burial ground used for unbaptised infants and others considered ineligible for consecrated ground under Catholic Church practice. These sites were typically placed on liminal land, and the choice of a townland boundary here is deliberate in that sense, positioning the dead at a threshold between one place and another.

Cillíní are found across Ireland in their hundreds, and for much of Irish history they occupied an ambiguous social and spiritual space. Because unbaptised children could not, under the theological conventions of the time, be buried in a parish churchyard, families interred them quietly in marginal ground: old ring-forts, cliff edges, the banks of streams, or boundaries like this one. The L-shaped outline at Killiath is an unusual detail; most such enclosures tend toward simple rectangular or oval forms, and the shape here may reflect the natural contours of the scarp or the line of pre-existing field boundaries. The set stones within, uncut and unlettered, are characteristic of the type, marking graves without identifying them.