SonicWALL ex9000 Getting Started page 42

Attaching Inner Rails to the Appliance
Use the following steps to attach the inner rails to the appliance:
1. Position the inner rail alongside the side of the appliance
with the finger tab facing outward.
2. Align the screw holes of the rail and the mounting holes of
the appliance and then attach the inner rail to the appliance
with crosshead threaded screws.
3. Repeat the above steps to attach another rail on the same
side of the appliance.
Page 40 Attaching Inner Rails to the Appliance
4. Attach the front bracket to the system.
5. Repeat to attach the other inner rails and front bracket to
the other side of the appliance.