There are times when your Mac may misbehave and refuse to boot into OS X. You may get a sad Mac face, an audible beep, or another ailment keeping your Mac from properly booting. It’s also open source, and you can download it for free. Open Karabiner-Elements from your Mac’s Applications folder. Select the “Simple Modifications” tab and click the “Add Item” button at the bottom of the window. Click the empty box in the “From Key” column and select the key that you want to change the behavior of. The Command key is the most common modifier key in Mac OS X. Many menu items, such as Quit, Close, and Save, have a keystroke shortcut using the Command key. To use such a shortcut, hold down one of the Command keys and press the letter key for that item. For example, to save a document in most applications, hold down Commmand and press s. You can also use Mac OS X shortcuts by pressing Command-Tab and then using the arrow keys to navigate to the Finder. If a Finder window was open, you go to that window. Otherwise, you go to the desktop. In that case, go to the menu bar by pressing VO-M or, if you’re using VoiceOver gestures, double-tapping near the top edge of the trackpad.
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