NEC Express5800/R120b-1 User Manual page 72

Installing Rail Assemblies
1.
Insert the square projection of the rail assembly into the angle hole on the 19-inch rack
until it is locked with clicking sound.
The figure below shows the right side (front) of the rack. Install the rail assemblies to the
right side (rear), and left side (front and rear) of the rack in the same procedure.
Make sure that the rail assembly is installed at the same level as the other slide rail
assembly already installed.
NOTES:
There may be some backlashes in the front and rear, however, it is
not a deficiency.
Make sure that the rail assembly is surely locked to the rack.
Setting Up Your Server 3-9