If you use multiple displays, this feature allows you to orient a particular monitor to fit your needs. The quickest way to do this is to simultaneously press and hold Ctrl + Alt together, then use a directional arrow to flip the screen. The right and left arrows turn the screen 90 degrees, while the down arrow will flip it upside down. Use the up arrow to bring the screen back to its normal position.

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These key commands only work with certain computers, so if you can't get them to work, you can go through Settings > System > Display, or right-click on the desktop and choose Display Settings to get there faster. Choose an option from the Display Orientation drop-down menu to turn your page around in all sorts of ways.