Remove the following screws from the back case and corner covers:

Eighteen 6 mm Phillips #0 screws

Two 7 mm Phillips #0 screws

If you do not have a magnet that can lift the screws out, you may have to turn the laptop over until each screw drops into your hand.

Do not proceed unless all the screws are out! You can severely damage your keyboard in the following steps if you still have a screw in place.