Oracle sun X4-8 Installation Manual page 43

Place the cage nuts on the inner-facing side of each rail. There should be two cage nuts in
each front rail and three cage nuts in each back rail.
4. Install the left and right shelf rails.
The rails are labeled left and right, front and back.
The rails have studs and a latch at each end. For each rail:
Expand the shelf rail to fit the rack.
a.
Install Shelf Rails and Back Mounting Brackets
Rack Installation Instructions 43