Asus RS120-E4/PA4 - Manual (Page 48)

Chapter 3: Installation options 3-4
3.4. Rackmounting.the.server
To mount the server to the rack:
1. Firmly hold the server on both sides and insert the rear panel side to the front
end of the rack rail, then carefully push the server all the way to the back until
the front panel fits the front end of the rack, and the rack screws on the server
match the middle hole on the rack..
2. Tighten the two rack screws to
secure the server to the rack.
Rack screw