Experimentalist

Hi I want to draw a freeform parallelogram to model an odd shaped patio. I want to draw it as a single line and close it by ending at the start point. Please see attached sketch. I know I can us the line tool and hold the shift key to snap to a straight line but how do I get a new point at a 90 degree or other angle with square not curved edges? What tool should I use? Is there a video that could help me? Thanks in advance