doc basically has it right, but it is hard to explain w/o using visual examples. the lines in one view correspond to events on the 3D object (sides, angles/points, etc.). these events obviously remain the same no matter which view you are looking at (they are fixed parts of the 3D object), so the lines representing them should demonstrate certain similarities between different views. like doc said, the verticals on top will also be verticals from the front. also, the horizontals on top will be verticals from the end. they don't have to be identical lines, since events will look different and therefore be represented differently from the different angles, but they do have to be there. therefore, the number of corresponding lines should remain the same.
i don't think that explanation made much sense, but i never liked event counting in the first place. it would usually only rule out one answer for me, maybe two if i got lucky, so i always found my time best spent just looking at the views and formulating the correct 3rd view in my mind, then finding it in the answers. if it works for you, though, go for it - i may have been doing it wrong or something
