This study deals with medieval views of the function of objets d'art in liturgy and the symbolism of church space. Its source is the Rationale divinorum officiorum, a liturgical handbook by Durandus of Mende (1230/1-1296) which was widely available in the Middle Ages. The first part treats the figurative hermeneutics of the Rationale and its premises in Augustine's doctrine of signs and in the symbolic universal system of Hugh of St. Victor. Its main section deals with the medieval system of rules for dealing with objects, particularly pictures, movable inventory and textiles. Using semiotic approaches an explanation is given of the functional significance of these objects of art in the context of the liturgy and its conscious "embedding" in ecclesiastical space. A special paradigm for the "correct use" of objects d'art is provided by the textiles much used in the Middle Ages. The Rationale shows an understanding of art which is representative of that period.