'If walls and floors and ceilings are the unrecognized boundaries defining our experiences of emptiness, doors or doorways embody a different function. They are less about the spaces in which we live than about our movement between them. Like staircases, they are areas or points of transition: from one room to another, from inside to outside, from private to public, from youth to adulthood. They signify spatial and temporal movement. We mark out our lives by passing through thresholds; youth pushes through doors in order to fulfill its promise, while age closes doors on one chapter after another. Yet at the same time doorways signify as barriers; against entry, or escape, or the real or the imagined threat of what lies on the other side. They can protect us from the world outside, but they can also keep us from the spaces we aspire to be' (R. Noble, exh. cat., Kunsthaus Bregenz, Rachel Whiteread, 2005, p. 70).