Corinthian Impost
The Corinthian impost differs from those of the other two orders in having a necking and necking moulding in place of the two unequal facias.
The total height should be divided into two, and the upper half divided into four. Then the top fillet and reversa moulding will be one of these divisions, the facia two, and the supporting ovolo will occupy the remaining one.
The lower half of the impost consists of a small torus and fillet beneath the ovolo, the necking, and the torus and fillet which form the necking moulding.