I think by bottom edge he means the actual bottom of the tremolo body.

Photo

The bottom of that should be parallel to the top of the body. You can see the slant of the top of the trem, if you make this level to the guitar body, the trem will be leaning back.


Oh, and Google threw this up... you can try it in future

www.ibanezrules.com/tech/setup/angle.htm

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