A bit more playing around reveals that if I push it just a little way, then enter the thickness of the wall, it does like it's supposed to. I guess I was pushing it too far, and not understanding what was happening.

Thanks for the help, folks.

OK, I'm really a newbie here. Started yesterday, in fact. Watched some of the intro tutorials, including the push-pull one. Here's the problem: I open a new drawing. Create a rectangle aligned on the green axis, say 6" by 10'. Pull it up to 8' tall (starting to see a wall here?) Now I draw a rectangle on the wall, starting at the floor, coming up 80" (a door?) Then using the PP tool, I push the door into the wall and when it gets to the back wall, it disappears, just like in the tutorial. But if I try the same thing with a rectangle not touching the bottom (a window), it doesn't work. It pushes out the other side, but never actually opens. I actually just now figured out that this was the distinction, and that this is the behavior when there's geometry in the way on the back side, but there isn't any here. What's going on here, and how do I make it make a window without having to play games like Edit|Intersect Faces|Selection and then delete the face that pushed through (sometimes works, but not always). SU is a nice toy, but I can see nowhere in the docs or tuts that address this.

Thanks in advance,
Ed