Asus ESC4000/IB - Manual (Page 40)

Chapter 2: Hardware setup 2-18
3. Firmly pull the PSU out of the
system chassis.
2. Hold the PSU lever and press the
PSU latch.
To install a second PSU
1. Hold the PSU dummy cover and
press the dummy latch.
2. Firmly pull the PSU dummy cover
out of the server chassis.