Formed by the panels at either side of 13th-century wooden crucifixes, below the arms, usually filled with painted images of Christ's Passion and Resurrection. An example is the apron in Coppo di Marcovaldo's Crucifixion in the Pinacoteca at San Gimigniano (second half of the 13th century). Sometimes the figures of the grieving Virgin Mary and St. John occupy this space, as in the Crucifixion by Berlinghiero Berlinghieri (early 13th century; Lucca, Pinacoteca). Later, Cimabue would cast the apron figures to the end of the arms of the cross and fill the space with decorative patterns to place all focus on the suffering figure of Christ. Examples are his Crucifixion panels at San Domenico, Arezzo (c. 1280), and at Santa Croce, Florence (1287-1288).
Historical dictionary of Renaissance art. Lilian H. Zirpolo. 2008.