It is roughly three metres across, built from drystone walling without mortar, and a small stream flows from it. What makes it quietly remarkable is not its current condition but what it once drew people to do: press pins, one by one, into the bark of an ash tree growing beside it, each pin a token of hope that a toothache might lift.

The practice recorded here belongs to a broader Irish tradition of votive offerings at holy wells, where water was believed to carry curative properties. Unlike many such sites, Finnrenashark had no pattern day, the festive annual gathering common at wells with a strong communal devotional life. Visitors came informally, drank the water, carried some away, and rubbed it on whatever part of them was in pain. The speciality was toothache. A schoolchildren's survey conducted in 1934, as part of the National Schools Survey of Holy Wells, captured a vivid account of the ash tree at the time: already old, its trunk partly dead and standing, but putting out new branches from the remaining wood. The bark, the account notes plainly, was thick with pins. By then the well appears to have been in decline; Reynolds, writing in 1977, described it as abandoned, with collapsed walling and dense briar cover. References in older sources, including Comerford in 1883 and O'Flanagan in 1933, confirm it was known and documented well before that.

The site lies to the north of Cannakill School, on the hillside approaching Croghan Hill. The dense briar growth noted in survey records makes it difficult to access, and there is no organised pathway or signage. The ash tree, so central to the well's ritual life, was already in a state of slow ruin in 1934; what remains of it now, if anything, is unclear.