Install the Square-Hole Adapter
The array and expanion self chassis require racks with square holes. The round-to-square hole adapters (4 pieces) must be installed onto the rails before installing the rails to the rack.
The rails must be attached to the chassis first, before attaching the square-hole adapter.
Cabinet rack holes are not evenly spaced. If you want to ensure that the thumbscrews align correctly, align the rack at the border of a unit. The middle rails attach to the front posts. The outer rails attach to the back posts.
To install the square-hole adapter: