Tabernacle covered by veil

Tabernacle signified in the Middle Ages sometimes a ciborium-altar, a structure resting on pillars and covered with a baldachino that was set over an altar, sometimes an ostensory or monstrance, a tower-shaped vessel for preserving and exhibiting relics and the Blessed Sacrament; sometimes, lastly, like today, it was the name of the vessel holding the pyx.

That is, at the present time in ecclesiastical usage it is only the name for the receptacle or case placed upon the table of the high altar or of another altar in which the vessels containing the Blessed Sacrament, as the ciborium, monstrance, custodia, are kept. As a rule, in cathedrals and monastic churches it is not set upon the high altar but upon a side altar, or the altar of a special sacramentary chapel; this is to be done both on account of the reverence due the Holy Sacrament and to avoid impeding the course of the ceremonies in solemn functions at the high altar. On the other hand it is generally to be placed upon the high altar in parish churches as the most befitting position ("Cærem. ep.", I, xii, No. 8; "Rit. rom.", tit. IV, i, no. 6; S.C. Episc., 10 February, 1579).

A number of decisions have been given by the Sacred Congregation of Rites regarding the tabernacle. According to these, to mention the more important decisions, relics and pictures are not to be displayed for veneration either on or before the tabernacle ("Decreta auth.", nos. 2613, 2906). Neither is it permissible to place a vase of flowers in such manner before the door of thetabernacle as to conceal it (no. 2067). The interior of the tabernacle must either be gilded or covered with white silk (no. 4035, ad 4); but the exterior is to be equipped with a mantle-like hanging, that must be either always white or is to be changed according to thecolour of the day; this hanging is called the canopeum (no. 3520; cf. "Rit. rom., loc. cit.). A benediction of the tabernacle is customary but is not prescribed.[1]