abacus

…square wooden block called an abacus, placed on the top of a post, and an oblong block called a billet, set with its greatest dimensions parallel to the beam above. Shaping the ends of such blocks produces a laterally spreading form of capital, which can be elaborated upon by multiplication…

…order to better support the abacus; and the abacus itself, a square block that directly supports the entablature above and transmits its weight to the rest of the column below.