Dell XPS 15 (L502X, Early 2011) - Manual (Page 42)

42 Hard Drive
7 Replace the four screws that secure the hard-drive assembly to the
computer base.
8 Replace the palm-rest assembly (see "Replacing the Palm-Rest Assembly"
on page 32).
9 Replace the battery (see "Replacing the Battery" on page 14).
CAUTION: Before turning on the computer, replace all screws and ensure that no
stray screws remain inside the computer. Failure to do so may result in damage to
the computer.