HPE ProLiant ML350 Gen11 User Manual page 76

3. Locate the orientation markers on the mounting rails:
The front end of the rails is marked FRONT
The rear end of the rails is marked with L L for left and R R for right.
4. Fasten the mounting rails to the rack columns:
a. Retract and hold the rear retention bracket (callout 1).
b. Insert the pins on the mounting flange into the rack column holes (callout 2).
c. Release the rear retention bracket (callout 3).
d. Retract and hold the front retention bracket.
e. Insert the pins on the mounting flange into the rack column holes.
f. Release the front retention bracket.
FRONT.
HPE ProLiant ML350 Gen11 Server User Guide 76