Abstract: The present invention provides top-bedding that has a head-end delimited by a head-end edge; a foot-end opposite the head-end, the foot-end delimited by a foot-end edge substantially parallel to the head-end edge; at least one pair of opposing sides delimited by side-edges; a first head-end corner and a second head-end corner; and a reversible expansion means for reversibly converting the top-bedding from a closed configuration to an open configuration, the closed configuration being approximately rectangular, and the open configuration having the shape of an irregular, simple polygon, whereby the distance between the first head-end corner and the second head-end corner is greater when the top-bedding is in the open configuration than when it is in the closed configuration.