They serve as the heraldic supporters flanking a coat of arms belonging to the St John family, and their presence is a reminder of how elaborate, and occasionally eccentric, the language of heraldry could be. The plaque is positioned near the east gable, carved with a plain border and inscribed simply, and plainly defiantly, THE ARMES OF ST. JOHN.

The shield itself follows the conventions of formal heraldry closely. Its field is ermine, the fur pattern associated with noble rank, and it bears a horizontal band across the top, known as a chief, on which sit three mullets, the five-pointed star shapes used in coats of arms. Above the shield rises a crest of a falcon in the act of taking flight, mounted on a wreath and resting atop a closed helm with mantling, the decorative cloth that in earlier centuries protected a knight's helmet from the sun and in heraldic art became increasingly stylised and foliate. The St John family were significant landowners in the Fethard area during the medieval period, and the placement of their arms within the abbey chancel, the most sacred part of the church, suggests a close relationship between the family and the religious community, whether as patrons, benefactors, or holders of burial rights within the building.