c.  Repeat steps a–b on the other inner rail.
3.  Locate the orientation markers on the mounting rails:
The front end of the rails is marked  FRONTFRONT.
The rear end of the rails is marked with LL for left and R R for right.
 
4.  Fasten the mounting rails to the rack columns:
a.  Retract and hold the rear retention bracket.
b.  Insert the pegs on the mounting flange into the rack holes.
c.  Release the rear retention bracket.