Hitachi DKC910I Installation Section page 39

Hitachi Proprietary
Rev.2
INST(IN)03-01-80
(6) Bring down two Clips on the front and rear edge of the rail.
(7) Fit Positioning Pins  and  of the rail (two pins in total on the front and back edge) into holes on
the right side of the rack at the position where you want to install the Drive Box.
(8) Raise the Clips of the rail to fix the rail to the rack.
Figure 3-8 Installing Rails
Right side of rack
Unit boundary
Unit boundary
Unit boundary
Positioning pin 
Frame (rear right side)
Rail
Clip
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Clip
DKC910I
Unit boundary
Unit boundary
Unit boundary
Positioning pin 
Frame (front right side)
[INST(IN)03-01-80]