Apple Xserve (Early 2009) - Manual (Page 13)

13 Chapter 1 Installing the Xserve
Step 2: Assemble the mounting rails
The Xserve comes with both short and long extensions that you combine with
standard front rails to create a pair of rails that are the right depth for your rack.
Long extension
Short extension
These pegs engage the
slots in the extension.
Rail
Slide a matching rear extension onto each of the two front rails. m
The extension goes on
the outside of the rail. Engage the pegs
in both slots.
This notch should
be on the bottom.
This end is up.