There are banks here, and ditches, and what might be the remnants of a fosse, the defensive trench typically cut across a promontory to turn a finger of land into a fortified enclosure. But whether any of it is the work of human hands or simply the product of coastal geology and erosion is, even after careful examination, genuinely uncertain.

A survey carried out in 2002 by Casey documented the site in careful, measured terms. The headland runs about 200 metres in length, widening to 90 metres at the neck before narrowing to 45 metres at its northern tip. Roughly 90 metres from that tip, there are possible remains of a stone and earthen bank with an external fosse cutting partway across the headland, and a second, lesser bank running parallel to it some 11 metres further inland. These could be the degraded defences of a promontory fort, a type of enclosure found widely along the Irish coastline in which a headland is sealed off at its landward end by one or more banks and ditches, effectively using the sea as a natural barrier on the remaining sides. Or they may not be. More striking still is a series of six parallel banks with intervening ditches covering much of the landward portion of the headland, features that could represent a more elaborate defensive arrangement, or could be entirely natural. The soil cover is thin and rapidly eroding, and the sea, though accessible from within the headland, is described as reachable only with difficulty.

What makes Tiduff genuinely interesting is precisely this ambiguity. The promontory fort is one of Ireland's more recognisable prehistoric and early medieval monument types, often dramatic in its cliff-edge placement, but the category depends on confident identification of at least some artificial construction. Here, that confidence is absent. The landscape holds the shape of something intentional without being willing to confirm it, which is perhaps its own kind of character.