Dell XPS 14 (L421X, Mid 2012) - Manual (Page 11)

After Working Inside Your Computer
After you complete replacement procedures, ensure the following:
• Replace all screws and ensure that no stray screws remain inside your computer.
• Connect any external devices, cables, cards, and any other part(s) you removed
before working on your computer.
• Connect your computer and all attached devices to their electrical outlets.
CAUTION: Before turning on your computer, replace all screws and ensure
that no stray screws remain inside the computer. Failure to do so may damage
your computer.
After Working Inside Your Computer | 11