Apparatus for supporting one or more cables in a generally vertical orientation comprises a support structure extending along a generally vertical direction and a plurality of support blocks positioned along the vertical support structure. Each of the support blocks has one or more cable openings defined therethrough. The support blocks comprise a plurality of first group support blocks and a plurality of second group support blocks. The cable openings of the first group support blocks are aligned with each other, and the cable openings of the second group support blocks are aligned with each other and horizontally offset from the cable openings of the first group support blocks.