The invention relates generally to adjustable shelf units typically used to provide workspace and storage space for electronic equipment.  In particular, the invention concerns adjustable shelf units which include at least one shelf supported by adjustable braces having horizontal support surfaces that remain horizontally disposed as the braces are moved to freely selectable elevations. 
Known shelving structures typically include braces coupled to vertical stanchions for supporting shelves.  These known shelving structures vary widely in terms of ease and extent of adjustability of the shelves.  For example, one group of known shelving structures requires tools and special fastening devices to secure the braces to the stanchions.  Another group of such structures has limited shelf adjustability in that the adjustable support braces can only be positioned at fixed locations along the vertical stanchions. 
Another example of known shelving structures is provided in U.S. Pat.  No.  3,865,337.  The disclosed structure includes slotted vertical stanchions in which braces are positioned.  The braces have a cantilevered end adapted to support a shelf and a connective end for locking the brace into a position.  This structure, while freely adjustable, requires a complicated procedure to adjust the position of each shelf.  A shelf to be adjusted must first be cleared of any equipment located thereon.  Next, the shelf (and underlying brace) must be rotated upwardly to release the locking mechanism at the connective end of the brace.  Once these two steps have been performed, the shelf (and brace) can be moved to a different position. 
It is an object of the invention, therefore, to provide a shelf unit with shelves which are easily adjustable to an unlimited range of elevations.  Another object of the invention is to provide such a shelf unit which can be easily and cost-effectively manufactured.