Components of the fitting system employed for connecting Parthenon's column drums. This system relied on three elements: two empolia and one polos. The former were placed in sockets curved in the centre of two adjacent vertebras’ interfaces. Empolia in the shape of a frustum had an aperture in their centre and were connected with a cylindrical vertical axe, the polos. This triple system facilitated the perfect fitting of the architectural members by aligning the drum centers and preventing the columns’ deformation in case of earthquakes.

The poles were made of wild olive tree or cornus wood and empolia of conifer wood.