The first step in reconstructing the boiler was determining how tall the brick base was by looking at the brickwork on the surviving jambs.  Specifically the Restoration Team was looking for areas of rough brickwork, because the brickwork that had once partially infilled the opening would have been interwoven with the brickwork on the sides of the opening.  When the masons removed the bricks in ca. 1881 the areas where they chopped out the bricks would have left rough, uneven patches of brickwork.  The height of these rough areas of brickwork therefore told the Restoration’s masons exactly how tall to build the boiler's base.  After the base was built, a design for the boiler was developed after looking at period examples and then constructed out of copper.