NEC Express 5800 User Manual page 146

Hardware
28. Adjust the support bracket corresponding to the rack length.
NOTE:
There are many holes on the support bracket so that it is
adjustable to be fit to the rack.
[1]Fix the arm at the place where the system can be pulled out from the rack completely.
As far as possible
[2]make sure not to hit each other when the arm is closed.
5 – 40mm depending on the rack size
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