Motorola ACE3600 RTU Owner's Manual page 27

Installation
4) Using the supplied two screws, attach the combined brackets to the metal upright of a 19"
rack unit. See Figure 2-7. Repeat on other side.
Metal Upright
Large Bracket
Small Bracket
Bracket Groove
Figure 2-7 Installation of Brackets for 19" Rack Units
2-7