if you were to look at an object from a side and take all the dimension from that view and draw it 2-D.....do this for all 6 sides of an object then you would have every dimension or be able to calculate every dimension from this drawing.....the drawings lay out in a way that allows you to fold it up like a cube and get all the dimensions using geometric laws.....it's the first type of drawings you learn in drafting classes....it's the basics of any mechanical drawings.....these are the things that will be so much more clear to you if you can take the classes...not trying to brow beat you w/ that but it really does make a huge difference in learning this stuff..I'll help you out w/ questions as long as I can answer them man but you're in for some head banging nights w/ this stuff on your own....
http://www.webpages.uidaho.edu/~sjung/lec2.htm
this seems to explain it better than I did
http://www.webpages.uidaho.edu/~sjung/lec2.htm
this seems to explain it better than I did