Abstract: The specification discloses a vertical framework structure extendable in both lateral and longitudinal directions. The structure comprises a plurality of vertical columns which are tubular members having a rectangular cross-section. At least two vertical opposing faces of the column are provided with a series of pairs of vertically and horizontally aligned spaced mounting slots. The structure further includes at least one lateral bracing member adapted to support a shelf, and extending between a pair of front and rear vertical columns. Each end of said lateral bracing member is formed with a pair of mounting lugs projecting at right angles to the plane of the bracing member, arranged in vertical alignment and spaced apart vertically a distance equal to the vertical spacing of the mounting slots on the column. At least one mounting lug has a locking means at the lower portion thereof. The horizontal bracing member has at a side surface thereof one or more upwardly extending shelf support flanges.