Dell PowerEdge 4220 Guide D'installation page 21

6 Rehang the front door by reversing the steps in "Removing the Front Door"
7 Reverse the lock catch.
Get user manuals: See SafeManuals.com
on page 8.
Unscrew the two Phillips screws that hold the lock catch to the vertical
a
frame member.
Remove the lock catch and rotate it 180 degrees.
b
Reinstall the lock catch on the other rack front vertical frame member
c
by aligning the holes of the catch with the holes of the frame member
and then reinserting the two Phillips screws.
Installation Guide
19