Remove the following 3 screws from the rear wall of the battery compartment:

Two 3 mm Phillips #00. (A1181 has three 3 mm screws and one 4 mm.)

One 4 mm Phillips #00 on the right side.

When reinstalling these screws, press gently on the lower case to line up the screw holes.

These screws easily strip, so be careful while taking these particular screws out.