Dell DR4300e Owner's Manual page 62

NOTE: The bezel key is attached to the back of the bezel.
2. Unlock the bezel by using the key.
3. Slide the release latch up and pull the left end of the bezel.
4. Unhook the right end, and remove the bezel.
Figure 9. Removing the optional front bezel
1. release latch
3. front bezel
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2. bezel lock