It is a jamb, the upright side-piece of what was once an arch, cut from fossiliferous limestone, meaning the rock itself contains the remains of ancient marine creatures pressed into its fabric over millions of years. The piece measures just 63 centimetres in length, modest enough to hold in two arms, yet its surface tells a more layered story than its size might suggest.

The jamb comes from Leggetsrath, a townland in County Kilkenny, and its most striking feature is what covers it. The soffit, which is the underside of the arch opening, along with the chamfered edges on either side, a chamfer being an angled cut made to soften what would otherwise be a sharp corner, are coated in a fine plaster render. Running horizontally across that render are three thin decorative bands, each roughly 15 millimetres wide and spaced some 22 to 25 centimetres apart. These are not structural; they are ornamental, a deliberate choice by whoever finished the stonework. Over time, a second, rougher render was applied on top of the fine one, suggesting the arch passed through at least two phases of use or repair before it was eventually removed from its original context altogether. Whatever building it belonged to, a church, a house, a gateway, is not recorded, but the care taken with those three small bands points to a setting where appearance mattered.