Apple Xserve Intel (Late 2006) - Manual (Page 13)

Chapter 1 Installing the Xserve 13
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.
1 Slide a matching rear extension onto each of the two front rails.
Long extension
Short extension
These pegs engage the
slots in the extension.
Rail
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.