The entrance, barely 0.8 metres high and half a metre wide, is low enough that you would stoop to enter. Above it, a lintel carries an engraving that has weathered into partial illegibility: 'Owen Egan of Knocknanuss erected this in honour of God and BL...AD...' with what appears, from a reading made by Grove White in the early twentieth century, to be the numerals '78' at the end. On either side of the entrance, carved figures look out from the stonework, one of them sometimes misidentified as a sheela-na-gig, those enigmatic medieval carvings of female figures found on Irish church buildings. This one, however, holds its arms raised and bent at the elbow, palms open, in what scholars recognise as the orant position, a posture of prayer common in early Christian art, and is thought to date from the later medieval period at the earliest. Its features are precise: almond-shaped eyes, a narrow mouth, a well-defined torso, and fingers individually rendered. The figure to the right of the entrance is more worn, circular-headed, wearing what appears to be a long garment, one arm at the hip and the other extended.

The story behind the structure comes from a 1934 account by Bowman, who records that Owen Egan was a mason who lost his sight and had it restored after paying rounds at the well. Paying rounds at a holy well means walking a prescribed circuit, often a set number of times, reciting prayers as an act of devotion or penance, a practice with roots stretching back through medieval Christianity and possibly earlier. In thanksgiving for his recovery, Egan built the stone covering that still stands. The well is dedicated to St Bridget and was traditionally visited on the first of February, her feast day, which also coincides with Imbolc, the old Irish seasonal marker of early spring. Bowman notes that rounds were also paid on Fridays, Saturdays, and Sundays, with Sunday rounds required before Mass, after which worshippers were expected to receive Holy Communion at Castlemagner church. Pilgrim crosses scratched onto the carved figures and onto other stones of the structure, along with votive offerings left around the well, make clear that people have continued to visit it for devotional purposes into recent times.