Dell PowerEdge 4210 Guide D'installation page 20

Figure 1-7. Rotate Front Door
6 Rehang the front door by reversing the steps in "Removing the Front
Door."
7 Reverse the lock catch.
Use the #2 Phillips screwdriver to remove the two #2 Phillips screws
a
that hold the lock catch to the middle horizontal frame member.
Remove the lock catch and rotate it 180 degrees.
b
Reinstall the lock catch on the new horizontal frame member by
c
aligning the holes of the catch with the holes of the frame member
and then reinserting the two #2 Phillips screws.
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Dell™ PowerEdge™ 4210 Installation Guide