What makes this promontory unusual is the feature that cuts across its narrowest point: a rock-cut fosse, meaning a trench carved directly into the bedrock, running on a north-south axis and measuring roughly five and a half metres wide and nearly two metres deep. That kind of earthwork is typically associated with Iron Age or early medieval promontory forts, where communities used a single barrier across the neck of a headland to turn a natural feature into a defended enclosure. Here, though, the story is a little more complicated.

The antiquarian Thomas Johnson Westropp, writing in 1914, noted that this particular trench was not purely prehistoric in origin. His reading of the site placed the fosse within the context of later medieval castle defences, suggesting it was cut or adapted to serve a castle recorded nearby. Westropp was a prolific documenter of Irish coastal fortifications in the late nineteenth and early twentieth centuries, and his observations, even where they remain unverified by excavation, tend to carry weight. The sub-rectangular shape of the promontory itself, combined with the deliberate cutting of stone rather than the piling of earth, points to a site where the landscape was worked and reworked across more than one period of occupation.