Entablature being called petrification. The structure of the entablature varies with the three classical orders: Doric, Ionic, and Corinthian. In each, the proportions of the subdivisions (architrave, frieze, cornice) are defined by the proportions of the column in the order. In Roman and Renaissance interpretations, it is usually approximately a quarter of the height of the column. Variants of entablature that do not fit these models are usually derived from them. Pure classical Doric entablature is simple. The architrave, the lowest band, is split, from bottom to top, into the guttae, the regulae, and the taenia. The frieze is dominated by
Tuscan order Italic architectural form, predating the Greek Doric and Ionic, associated by Serlio with the practice of rustication and the architectural practice of Tuscany. Giorgio Vasari made a valid argument for this claim by reference to il Cronaca's graduated rustication on the facade of Palazzo Strozzi, Florence. Like all architectural theory of the Renaissance, precedents for a Tuscan order were sought for in Vitruvius, who does not include it among the three canonic orders, but peripherally, in his discussion of the Etruscan temple (book iv, 7.2–3). Later Roman practice ignored the Tuscan order, and so did Leon Battista Alberti in "De