major churches, such as Albi Cathedral in France, inserted transverse screens in the later medieval period, or reconstructed existing choir screens on a greatly increased scale. In Italy, massive rood screens incorporating an ambo or pulpit facing the nave appear to have been universal in the churches of friars; but not in parish churches, there being no equivalent in the Roman Missal for the ritual elaborations of the Use of Sarum. The screen and Tridentine worship The decrees of the Council of Trent (1545–1563) enjoined that the celebration of the Mass should be made much more accessible to lay worshippers; and this was widely interpreted as requiring the removal of rood screens as physical and visual barriers, even though the council had made no explicit condemnation of screens. Already in 1565, Duke Cosimo de' Medici ordered the removal of the tramezzi from the Florentine friary churches of Santa Croce and Santa Maria Novella in accordance with the principles of the council. In 1577 Carlo Borromeo published , making no mention of the screen and emphasizing the importance of making the high altar visible to all worshippers; and in 1584 the Church of the Gesù was built in Rome as a demonstration of the new principles of Tridentine worship, having an altar rail but conspicuously lacking either a central rood or screen. Almost all medieval churches in Italy were subsequently re-ordered following this model; and most screens that impeded the view of the altar were removed, or their screening effect reduced, in other Catholic countries, with exceptions like Toledo Cathedral, Albi Cathedral, the church of Brou in Bourg-en-Bresse; and also in monasteries and convents, where the screen was preserved to maintain the enclosure. In Catholic Europe, parochial rood screens survive in substantial numbers only in Brittany, such as those at Plouvorn, Morbihan and Ploubezre . Symbolic significance The rood screen was a physical and symbolic barrier, separating the chancel, the domain of the clergy, from the nave where lay people gathered to worship. It was also a means of seeing; often it was solid only to waist height and richly decorated with pictures of saints and angels. Concealment and revelation were part of the mediaeval Mass. When kneeling, the congregation could not see the priest, but might do so through the upper part of the screen, when he elevated the Host on Sundays. In some churches, 'squints' (holes in the screen)