Measuring roughly half a metre square and only seventeen centimetres high, it was deliberately inserted into the wall directly in front of the entrance to what researchers call Cell A, one of the early monastic structures clustered around the island's church. On its upper face sits a centrally placed socket, approximately eighteen centimetres long and six centimetres wide, intended to hold the upright shaft of a cross that no longer survives. The positioning is deliberate and meaningful: a cross marking a threshold, framing the act of entering a sacred cell.

High Island, known in Irish as Ard Oileán, was home to an early medieval monastic community, and its remains include a church, clochans, and various enclosures. A clochan is a dry-stone corbelled hut, the kind of small beehive-shaped cell associated with early Irish monasticism, where individual monks would have lived or prayed. Cell A sits to the north of the church, and the cross-base was recorded by Scally in 2014 as part of a detailed survey of the island's monastic complex. The base itself is rectangular and relatively modest in its dimensions, but its placement at the cell entrance suggests it served a ceremonial or devotional function, marking passage into a space of particular religious significance. The cross it once supported is long gone, leaving only this socketed plinth as evidence of what stood there.