In the burial ground known as Killeen Cormac, near Colbinstown in County Kildare, there sits a granite block that is, in a precise sense, only half a cross. It tapers from a broad rectangular base up to a square top, and at that top there is a carefully cut mortice hole, a square socket designed to receive the upright shaft of a standing cross. The shaft itself is long gone. What remains is the base alone, a thing built entirely around an absence.

There are in fact two such objects recorded in this burial ground, and scholars have debated which is which. The one in question was documented by Fitzgerald between 1899 and 1902, at a time when antiquarians were beginning to systematically catalogue early Christian monuments across Ireland. The block measures 0.73 metres in height, with a base of 0.44 metres north to south and 0.34 metres wide, narrowing to a 0.2 metre square at the top where the mortice socket sits. That socket is 0.1 metres deep, and its eastern side has broken away at some point, leaving the mouth of the joint open to the weather. A mortice-and-tenon joint of this kind, where a shaped stone cross shaft would have been fitted into a prepared socket in a separate base, is a recognised feature of early medieval Irish stone crosses, allowing large monuments to be assembled from separate carved pieces rather than cut from a single block. That the shaft is missing here is not unusual; many such crosses survive only in fragments, their components scattered or repurposed over centuries.