NEC UX5000 Hardware Manual page 63

Chapter 1 - Installing the KSUs
3. For the plastic KSU-B/E units, attach the 2 bar brackets at the correct positions on the rack. These will
be used to secure the KSUs to the rack in their proper vertical position.
Figure 1-61: ATTACH TOP AND BOTTOM BAR BRACKETS
Chapter 1 1 - 53