I'm trying to extrude multiple rectangles that share a line or two with another rectangle. They are made by defining points as the corners in a 3d sketch then joining the points with lines. I have an example attached. The first rectangle is easy enough to extrude but the second almost always grabs 3 lines instead of 4 and calls it an open contour or will try to grab more than one rectangle at a time. Is there a different tool I need to use or a better way to define them? Thanks!
I was extruding them along the defined axis toward the defined plane.
To start with, you're making this much more difficult than it needs to be. In fact, I don't know if it's possible to accomplish what you're trying to do with the workflow you described, but it's easy enough to accomplish with another one.
One of the most important things when learning SW is never use a 3d sketch when a 2d sketch will get the job done. I assume you imported that 3d sketch from somewhere, so I started a new sketch on your Plane 1, and used the "Convert Entities" sketch tool to project your 3d sketch into the new sketch. Then I extruded one area, choosing "Up to Vertex" and choosing one of the points from your 3d sketch to define the end condition. Selecting the desired contour from a 2d sketch is a simple matter. (The green lines are your 3d sketch, and the black ones are from my 2d sketch.)