The manual is a good source for a lot of information. However, I often find it lacking enough details about specific field elements to answer all my questions. If you need exact specifications, I suggest looking at the game field drawings located here:
http://www.usfirst.org/sites/default...c_Drawings.pdf
Don't look at the team drawings, because those often deviate from the real field dimensions to make it "easier" for teams to build them.