Measuring just 0.6 metres high and 0.54 metres wide, it carries a Holy Trinity carving in high relief, the figures pressing outward from the stone surface by up to 0.16 metres. One corner has been broken away, and the panel has clearly travelled, but what remains is a remarkably detailed piece of late medieval craftsmanship that has ended up, somewhat by accident, in a 19th-century porch.

The panel was moved to its present home in the early part of the 19th century from the medieval church of St Mary's, located roughly 190 metres to the northeast on Green Street. It is thought to have originated in a chantry, a small chapel endowed for the saying of prayers for the souls of the dead, within that church, one dedicated to the Holy and Undivided Trinity of St Catherine. The art historian Helen Roe attributed the carving to Rory O'Tunny, a sculptor working in the Irish medieval tradition. The scene depicted is a Throne of Grace Trinity, a composition in which God the Father holds the crucified Christ before him, with the Holy Spirit as a dove placed between the Father's beard and the arms of the cross. God sits on a bench-like throne wearing, as Roe describes it, a low diadem with six fleurons that, when seen from above, reads as a multi-petalled rosette, possibly representing a fabric cap beneath. His hair falls in two broad swags to his shoulders, his beard is arranged in three neat coils, and he wears a pleated alb under a voluminous mantle with what appears to be a fur-bordered shoulder cape. His right hand, now partly broken, once offered a gesture of blessing; his left supports the end of the crossbeam. Christ is shown with arms straining from the nailed hands, the body pulled downward by its own weight, legs contracted at the knees, feet crossed and pierced by a single nail.

The panel is accessible to anyone who approaches the church porch, and the scale of it, modest enough to overlook, makes the density of carving all the more surprising at close quarters. The damage to the upper dexter corner means the Father's blessing hand is largely lost, but the dove, the coiled beard, and the strained figure of Christ remain legible and, in their detail, quite arresting.