Abstract: An end support unit for supporting the ends of at least one front and one rear cross beam including: a front support post having a column of slots along its length for receiving at least one slot engaging member of the front cross beam; a rear support post having a column of slots along its length for receiving at least one slot engaging member of the rear cross beam; an upper brace fixedly extending from the upper end of the front support post to the upper end of the rear support post; a lower brace fixedly extending from the lower end of the front support post to the lower end of the rear support post; and a diagonal brace extending diagonally between the front support post and the rear support post.