Okay, so bear with me. I'm not actually involved with model railrods (although they DO look interesting ), but my father is getting into it. Since he's new he obviously has lots to learn, but the one thing he doesn't get is the whole 'percent' thing. He knows that if he wants to introduce a grade he shouldn't go too much over 2% (at least for now, I suppose). Unfortunately, he has no idea how to measure, build, etc. within this 2%. My thought was that it has something to do with those little half circles you used to have in school, but I wouldn't bet money on it. And I of course thought 'who uses all that trigonometry after school'.