Sitting in the graveyard of St. Peter's Roman Catholic Church at Two-Mile-House in County Kildare is a heavy, bowl-shaped stone that nobody can quite agree on. It is too large to be a water stoup, the small wall-mounted basin used for holy water at a church entrance, and its proportions rule out identification as a bullaun stone, those shallow, cup-marked boulders found at early Christian sites throughout Ireland. It has no drainage hole, which complicates the most obvious reading of all, that it was once a baptismal font. What it actually is remains genuinely open.

The stone measures roughly 64 centimetres across at the outer rim, with a circular basin 44 centimetres wide at the top, narrowing to 17 centimetres at the base, and sinking about 21 centimetres deep. Those proportions are substantial, and scholars have noted that several large, plain, unperforated bowls of this type, initially catalogued as fonts, were later reconsidered as medieval mortars, the kind used for grinding or preparing materials in a domestic or ecclesiastical context. Given that Herbertstown Church once had a resident priest, and that the adjoining Herbertstown Castle stood nearby, the stone could plausibly have served either household. Helen Roe raised this possibility as far back as 1968 in relation to comparable stones elsewhere in Ireland. At some point before 1990, local parishioners removed the stone from Herbertstown Church and brought it to Two-Mile-House, where it has remained since, catalogued by William Gibson in 1990.