To determine the spacing of the ornaments on the chair rail the total length of the rail was divided by 150.  Because these rails were also often intended to have fluting caved into them to  mimic the trigylphs and metopes that are found on classical Doric friezes, flutes were also specified for the Montpelier chair rail.  These flutes were common in late 18th and early 19th century Virginia and the chimneypiece at Arlington House that held the oval ornament reproduced for Montpelier also featured carved trigylphs.  To create the effect at Montpelier, the restoration carpenters carved four wooden flutes into the chair rail between the composition ornaments.