I need to rotate the red rectangle at the same angle as the black lines.
How can I adapt to the way the automatic way align objects to each other. Is there a way to get around this?
Animation 1: Screen capture of procedure above.
Alternate method draw a new line on top of the line with line tool. Alt click with line tool to get the angle. Rotate your grid to that angle. Redraw square.
* In general if you do not use the white arrow then you will have a very hard time doing a really big part of all that Illustrator does.