The retablo is an art form that flourished in colonial Mexico, reaching the height of its popularity in the latter part of the 19th century. Painted primarily by provincial, untrained artists on inexpensive materials such as copper, tin, and wood, these small works depicted scenes using symbolic, allegorical, and religious imagery. Often unsigned, retablos were sometimes commissioned by individuals, but were most frequently sold by peddlers door to door or at churches during festivals. Figures on retablos are depicted in such a way that holy persons and saints are identifiable from their costumes and attributes. A three-quarter view is almost always used to depict a holy person. The remaining imagery is usually shown in size according to a hierarchical scale of importance.