[Fractint] newbie question

Hi: I am new to this. I want to create a skyline pattern of rectangles. I know I need the L System grammar. I am just not sure about the specifics. Below is a crude example of what I am talking about. Any advice on algorithms, names, and driections for solving the problem would be helpful. start with a line ___________ one iteration ___ ___| |___ two iterations _ _ _| |_ _ _| |_| |_| |_ J.