It is not the elegant carved stonework associated with more prominent ecclesiastical sites. Instead it is a squat, blunt object, roughly rectangular in granite, with rounded corners and a shallow bowl barely fifteen centimetres deep. At the centre of that bowl is a small square drain-hole, eight centimetres across, through which water would have passed after use. A holy water stoup, a small vessel used to hold blessed water, rests inside the larger font, the two objects sharing the same patch of floor where they have apparently remained long after the church itself fell into ruin.

The font measures roughly ninety centimetres by eighty centimetres at its widest, and stands only thirty-seven centimetres high, giving it a low, almost table-like profile. The rim is a substantial eighteen centimetres thick, which lends the piece a solid, utilitarian quality. Granite is not the easiest stone to carve with precision, and the crudeness of the form may reflect both the material and the modest resources of whoever commissioned it. A baptismal font was a liturgical necessity in any parish church, the fixed vessel in which the sacrament of baptism was administered, so its presence here confirms that Grangesylvia functioned as a working parish at some point during the medieval period, even if little else survives to tell that story in detail.