This is a fast and inexpensive sketch technique for both linear and non-linear applications often used in the start of a design process. It generates many possible solutions and gives you a dynamic and simulated user experience.
We were asked to test out this sketch technique in making a coffee machine that had sertain specified functions. At first it felt wierd to used simple post-it notes to simulate user sequenses. I didn't know what to put where and so on. It just felt clumsy and I'd rather do the puzzle in my head. But ofcourse this is a useful technique, especially as the interface grows more complex. The practical performance needs to be exercised further though.