Have you ever needed to meet with students one on one but have a difficult time keeping them in order, or reminding them that they cannot come up to you until you're ready to help them? The help desk is the solution to your problems. Print the numbers at the end of the presentation, laminate them. Teach students to grab from the top of the card pile, then project your presentation. Call students up by number. This is a great management tool, and it will attract attention from your students as the transitions are pretty flashy.