In this detail the circular guideline drawn with a compass, which sets out the distance between flutes, is clear at the bottom. A second circular line can be vaguely made out which marked out the point to which roughing-out of the flute was carried up to before careful finishing began. The two vertical lines which determine the final edge of each flute can be seen at the top; the one on the left has a hole at its end from which a plumb line was probably suspended. Several horizontal lines can also be made out: one which marks the point at which the curve at the top of each flute begins and another which marks the apex of this curve. All of these marks are incised on a surface which has already been carefully smoothed.
In this image a coating on the stone known as scialbatura can also be seen; whether this was a coating applied to the stone or a naturally occurring patina is debated but it is a common feature on monuments in Rome.