I can't seem to figure out how to extrude from a rotated work plane. I have also had a lot of trouble just trying to get work plane to rotate 45 degrees. I have tried using the custom work plane button, but its very hard to figure out which angle I want and express it in WCS coordinates. When i finally got it rotated, it extruded my object down to the correct length, but it was rotated back to the default work planes angle.