A flat piece of mica schist, just over a metre long and roughly two thirds of a metre wide, bears an incised cross whose four limbs do not meet at the centre. Whether this reflects an early carving convention, an interruption in the work, or a deliberate theological or artistic choice is not recorded anywhere. The gap simply sits there, at the heart of the design, quietly refusing to resolve itself.

The slab was catalogued by Patrick Healy in a 1972 survey of ancient monuments at Glendalough carried out for the Office of Public Works. Healy recorded it as approximately rectangular, around ten centimetres thick, and positioned to the south-west of the structure known as the Priest's House, one of the smaller Romanesque buildings within the monastic enclosure at the valley's upper lake. A more precise measurement taken in 2005 placed the stone some three metres east-south-east of the south-east corner of that building. Mica schist is a locally available metamorphic rock, characterised by its layered, slightly glittering surface, and it was used across the Wicklow uplands for early medieval carved monuments. Cross-slabs of this general type, flat stones bearing incised crosses rather than the fully carved high crosses more familiar from sites like Monasterboice, are among the most common yet least remarked-upon survivals of early Christian Ireland.

The Glendalough site, known historically as Sevenchurches after the number of ecclesiastical buildings once clustered there, draws considerable visitor numbers to its round tower and cathedral. The Priest's House, near which this slab lies, is a smaller and less immediately legible structure, and the cross-slab itself is the kind of object easily passed without a second glance. Knowing to look for the incomplete cross, and to consider why those lines were cut to stop just short of meeting, makes it considerably harder to walk past.