Now eyeball it holding the roll of tape and lay it down along the pencil line. It may take a couple of tries to get it right. You can't just put in on the car a few inches at a time following the line as it will curve. Then you won't get your body lines straight.
Mastering a pull-up is no easy feat, especially when you consider all of the mechanics involved with this exercise. While pull-ups appear to rely solely on upper body strength, it also puts a demand on your abdominal muscles to support your body and help maintain the correct form throughout the entire movement. Practice tightening your stomach muscles to get a feel for what engaged abdominal muscles are and tie that together with the steps of a pull-up to keep your body straight. Crossing your feet and bending your knees will help as well.
Stand with feet wider than shoulder-width apart and your toes slightly turned out. Keep the upper body straight and bend the knees into a squat slowly. Lower yourself as far as you are comfortable but make sure the knees are parallel with the toes. Push into your heels as you bring yourself up to the starting position.