Row Spacer comes with all necessary hardware. Row spacers are required for taller back to back rows. And spaced no more than 10' apart. To find the correct size, make sure you have 6" of clear flue space between pallets. For example, if using 48"D pallets, on 42"D uprights, a 12" Row Spacer will be the correct choice.  
For placing rows with building columns between them, please make sure to consider that in your selection.