The decorative pattern carved beneath the base of its cross is not centred. Whether this was a mason's error, a deliberate choice, or simply the result of working within the grain and limits of the stone, nobody now knows. It is a small asymmetry, easy to overlook, but it lodges in the mind once noticed.

The slab, which measures roughly 1.27 metres by 0.45 metres, was recorded by the scholar R. A. S. Macalister in 1916 to 1917, who placed it in the twelfth century on stylistic grounds. A cross-slab of this kind is exactly what the name suggests: a flat stone, usually recumbent or upright, incised with a cross rather than carved in three dimensions. This one carries a Latin cross rendered in double lines, with hollowed angles where the arms meet, and a rectangular base. Beneath that base sits the puzzling motif: an inverted triangle flanked on either side by series of oblique lines. The combination of the clean, formal cross above and this looser geometric arrangement below gives the stone an oddly layered quality, as though two different hands, or two different intentions, met somewhere in the middle. A drawing by de Paor survives in the site's records, preserving the detail of the composition for those who cannot make the crossing to the island itself.