Specifically the restoration team used stair at Castle Hill to help with the design of the balusters, railing and newels for the ca. 1764 stair.  While the new design did not exactly copy the originals from Castle Hill, it was largely based on the proportions of the Castle Hill stair and used the same “architectural grammar” (the proportions of the decorative elements and how they are assembled).  As a result, the conjectural railing clearly reflects what contemporaries of Madison’s father would have recognized as an appropriate and stylish railing even if it is not an exact reproduction of the railing that was installed in the house in ca. 1764.