Have you used "W" and "B" in PowerPoint?

How many times have you been in a presentation and someone asks a question. Then, you have to turn the projector off so you can use the board (which is right behind the projector's screen). You answer the question and now you need to wait another 30 seconds for the projector to start and to continue with your presentation. Did you know that while in your PowerPoint presentation you can press the letter "B" in your keyboard and the screen will go black? That way you do not have to turn the projector off. If you would like to have a white screen you can also press "W". Pressing "B", "W" or any other letter will go back to your PowerPoint presentation. You can use the same trick at the beginning of presentations to avoid people "peaking" at your presentation or getting distracted by the nice plots on the slides while you are trying to catch their attention.