Adding Controllers in the rack requires you to install rack rails in the rack and slide rails on the chassis for each Controller that you plan to add.
Controller rail kits can be installed in the Sun ™ Rack 900, the Sun Rack 1000, and third-party ANSI/EIA 310-D-1992 or IEC 60927 compliant racks with the following types of holes:
Square
Round
Threaded
Figure 1 Examples of supported rack holes 
- Legend
1 Square holes 2 Round holes 3 Threaded holes
Caution
Oracle recommends that you install each Controller after you install the rail kit before installing the next combination of rail kit and Controller. Installing all of the rail kits and then inserting the Controllers is not always possible because of potential space limitations at some data centers. Also, you run the risk of not placing the Controllers in the correct rack position and causing possible cabling issues. Note: Controller rails are packaged within the Pilot shipping carton (not the Controller shipping carton). Ensure that the Controller rails are not misplaced during unpacking.