It measures roughly 10.5 centimetres by 5.5 centimetres, barely larger than a palm. Yet this unassuming feature, lightly incised into the end of a long rubble stone close to the south window, is considered the most westerly mass-dial in Europe.

A mass-dial, also called a scratch dial, is a simple medieval timekeeping device: a set of radiating lines scratched into an exterior wall, with a central hole into which a priest would insert a gnomon, a small peg or rod. When the gnomon was placed at a right angle to the dial, it cast a shadow across the lines, indicating the hour and allowing the clergy to determine when to celebrate mass. The Cloghane example has eight such radiating lines spreading from a central socket, and follows the hemispherical form typical of the type. In England, thousands of these dials have been recorded on church walls, and they are a reasonably well-documented feature of the medieval landscape there. In Scotland, Wales, and Ireland, however, they are rare to the point of near-absence. Scholars have noted only a handful of Irish examples, which makes the Cloghane dial something of an outlier, a western European edge case in the most literal geographical sense.

The dial sits just 0.6 metres above the grave of the Deady family, and as of the 2010 survey carried out by Laurence Dunne, it was under constant threat of concealment from dense ivy growth on the church wall. Anyone hoping to find it should come prepared to look carefully at the stonework of the south elevation, and to clear a little vegetation if necessary. M. L. Harley, writing on Irish medieval sundials, recorded the diameter at approximately 150 millimetres, a detail that gives some sense of how easy it would be to overlook entirely.