Thanks for the info. What I meant about the components breaking the plane is this: There is a 3 story building, the window components are in at the first floor and do cut the plane correctly... when I copy them up to the next floor, they do not cut through there. If that's what your answer was for, my misunderstanding and thanks.

I can't get some of the simplest commands to work right - like copying window/door components within the same plane, and they don't all cut through the wall. With a symmetrical building, can half be drawn and the whole entity be mirrorred? Also am getting ready to tackle topography - any tips would be appreciated.