Dell OptiPlex 390 (Mid 2011) - Manual (Page 14)

Installing The Front Bezel
1. Insert the four hooks along the bottom edge of the front bezel into the slots
on the chassis front.
2. Rotate the bezel toward the computer to engage the three front bezel
retention clips until they click into place.
3. Install the cover .
4. Follow the procedures in After Working Inside Your Computer .
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