Window Duplicator is a helpful app which assists you during presentations. You no longer need to expose your screen or contort your body. Just select the desired window in Window Duplicator. A preview is instantly visible only for you. This helps you to ensure that this is the right window. For example if you have multiple instances of the same application open. After you have verified that this is the desired window, just hit play. The selected window is now duplicated onto the second display. Furthermore, the window on the projected screen is adjusted to the screens size. By resizing the original window, on you screen, you can affect the size on the projected screen. A window on the projected display is only scaled down. Scaling it up is up to you.