Elongate bodies for use in providing architectural and structural features in pre-cast panels are provided. A vent hole is drilled from the external surface of the laminate into the defect proximate to an opposite boundary from the fill hole. According to this method, magnetic heads included in the workpiece can be stably polished. The reflective portion reflects light from a light source forward through the lens, while the heat sink portion conducts heat from the reflective portion and dissipates the heat from the assembly.