The Metro 9995Z "S" Hook for Wire Shelving is an accessory S hook for use with the Super Erecta® and Hi-Rise Shelving Systems. The S hook is used to add on shelving units with only two posts required. Hook goes over the edge of the post-supported shelf and under the edge of the add-on shelf. Can be used to join units end-to-end, back-to-back or at right angles. Two S hooks required for each connection.