Such screens are derived ultimately from the oriental iconostasis

Chancel barriers with an architrave (templa) gradually replaced waist-high chancel screens and became the common type of barriers separating the altar area from the nave in the 10th century onwards, especially in Greece and Asia Minor, e.g. in the mid-10th — mid-11th century church at Xanthos, in the 11th century katholikon of the Monastery of Hosios Loukas, and in the katholikon of several monasteries of Mount Athos where this type of a chancel barrier with an architrave has been preserved behind a high iconostasis added later [10; 29, pp. 127–135; 44].

There is no consensus among scholars whether curtains were drawn in the intercolumnar
spaces of the templon, or when wooden icons began to be inserted in these spaces. Some scholars claim that in the 11th century, curtains were shut in the intercolumnar spaces to conceal the altar area at certain moments of the liturgy [28, pp. 36, 39], but both Matthews [33, p. 163–171; 34, p. 126] and Bortoli-Doucet [8, p. 44] contend that this is not substantiated by archaeological and liturgical evidence and the liturgy remained perfectly visible for the faithful. Chatzidakis [12], followed by Mango [32, p. 40], is of the opinion that icons were already introduced in the intercolumnar spaces in the 11th century, but Lazarev [29, pp. 130–136] believes that in Russia these spaces remained free of icons until the 14th century. Holy personages were represented on the templa of the 11th–13th centuries, but these were placed on the columns flanking the templon (generally made of fresco or mosaic), or painted on small wooden icons which were
set upon the top of the architrave [11; 13; 16, pp. 2–10; 3, p. 353]. This apparently continued to be so in most of the churches of the 13th and 14th centuries, e.g. the 13th century templon of the south Church of the Pantocrator (Zeyrek Camii) at Constantinople [16, p. 4, fig. 1; 14, p. 109, fig. 4]. Even in the early 15th century, the description by Symeon of Thessaloniki of a templon decorated with figures of Christ, the Virgin, John the Baptist, angels, archangels, saints, and apostles would refer to the architrave, according to Lazarev [29, pp. 135–140], or to the columns flanking the door of the templon, according to Walter [48, pp. 251, 266].

In the late 14th and 15th centuries, the icons, particularly those executed in Russia, grew
in size and the transparency of the early chancel barriers became gradually more and more opaque. The last evolution, the creation of a solid screen which totally cuts off the sanctuary from the nave and prevents the faithful from glimpsing at sacerdotal proceedings behind the screen, became standard in the 15th century in Russia.

In Early Christian architecture the templon was a barrier dividing off the sanctuary from the rest of the church; in Eastern Christianity this developed into different arrangements from those of the Western church, with the sanctuary often not visible by the congregation. In the West the ciborium, an open-walled but usually roofed structure sheltering the altar, became common, and was originally fitted with curtains that were drawn and pulled back at different points in the Mass, in a way that some Oriental Orthodox churches still practice today.

A large (or "deep") chancel made most sense in monasteries and cathedrals where there was a large number of singing clergy and boys from a choir school to occupy the choir. In many orders "choir monk" was a term used to distinguish the educated monks who had taken full vows, or were training to do so, from another class, called "lay brothers" or other terms, who had taken lesser vows and mostly did manual tasks, including farming the monastery's land. These usually sat in the nave, with any lay congregation.

Following the exposition of the doctrine of transubstantiation at the fourth Lateran Council of 1215, clergy were required to ensure that the blessed sacrament was to be kept protected from irreverent access or abuse; and accordingly the area of the church used by the lay congregation was to be screened off from that used by the clergy. This distinction was enforced by the development of canon law, by which the construction and upkeep of the chancel was the responsibility of the rector, whereas the construction and upkeep of the nave was the responsibility of the parish. Barriers demarcating the chancel became increasing elaborate, but were largely swept away after both the Protestant Reformation and then the Counter-Reformation prioritized the congregation having a good view of what was happening in the chancel. Now the low communion rail is generally the only barrier; despite being essentially a Counter-Reformation invention, this has proved useful and accepted in the Protestant churches that dispense communion. However the screen enjoyed a small revival in the 19th century, after the passionate urgings of Augustus Pugin, who wrote A Treatise on Chancel Screens and Rood Lofts,[7] and others.