Acer Altos R720 Series - Manual (Page 50)

3 System upgrade 40
Removing and installing the top cover
To remove the top cover:
1 Observe the ESD precautions and pre-installation instructions
described on page 35.
2 Remove the screw located on the top cover (A).
3 Press and hold the blue release button (B), then slide the cover
toward the back of the chassis until the cover disengage with the
slots on the chassis (C).
4 Insert your finger in the notch (D), then lift the top cover away
from the server and put it aside for reinstallation later.