When a friend bought his first Class A, like most of us he had a hard time judging where he was in his lane. Driving through traffic with white knuckles, frantically looking every which way, a bug hit his windshield. He realized the dead bug was exactly in the right spot for lining up his rig with the road line! He swore he'd never wash that windshield because now he was able to line up in the center of his lane! He put a dot on the inside with permanent marker and for all I know that spot is still there!
Sure beats all the prep needed for this advertised device! Put a dot to line up with both sides and you have your very own guidance system!