Altarpiece two, three, and multiple panels respectively. In the thirteenth century each panel was usually surmounted with a pinnacle, but during the Renaissance, single panel, or "pala", altarpieces became the norm. In both cases the supporting plinth, or "predella" often featured supplementary and related paintings. If the altar stands free in the choir, both sides of the altarpiece can be covered with painting. The screen, retable or reredos are commonly decorated. Groups of statuary can also be placed "on" an altar. A single church can furthermore house several altarpieces on side-altars in chapels. Sometimes the altarpiece is set on the altar
Early Netherlandish painting reflection and prayer was encouraged and the small-scale diptych fitted this purpose. It became popular among the newly emerging middle class and the more affluent monasteries across the Low Countries and northern Germany. Ainsworth says that regardless of size, whether a large altarpiece or a small diptych, Netherlandish painting is a "matter of small scale and meticulous detail". The small size was meant to entice the viewer into a meditative state for personal devotion and perhaps the "experience of miraculous visions". Late 20th-century technical examination has shown significant differences in technique and style between the panels of individual diptychs. The