Apple MacBook (13-inch, Mid 2009) - Manual (Page 39)

Chapter 3 Boost Your Memory 39
4 Insert the new memory modules in the slots:
a Insert the gold edge first, with the notch on the left side.
b Use two fingers with firm, even pressure to push in the memory modules.
You should hear a click when the memory is inserted correctly.
Note: The new memory module may have some residue on it from a lubricant
that makes the memory easier to install. The residue is normal and should not be
wiped off.
c If the levers don’t return to the closed position, move them to the right to
close them.
Notches
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