Asus RS120-E4/PA4 - Manual (Page 46)

Chapter 3: Installation options 3-2
3.1. Rackmount.rail.kit.items
If you have the rackmount rail kit, it contains two pairs of rails (one pair for each
side of the barebone system), and eight (8) pairs of nut-and-bolt type screws.
3.2. Rack.rails.assembly
To assemble the rack rails:
1. Determine the depth of the rack where you wish to install the system.
2. Match one long and one short rail to your desired length, and fix them
together using four (4) pairs of nuts and bolts.
3. Repeat step 2 to assemble the other rail pair.
Nuts
Bolts
Left pair
Right pair
Front ends
Rear ends
Nuts on outer side
Bolts on inner side