Hold down the Option key (also known as the ALT keyALT keyThe Alt key Alt (pronounced /ˈɔːlt/ or /ˈʌlt/) on a computer keyboard is used to change (alternate) the function of other pressed keys. Thus, the Alt key is a modifier key, used in a similar fashion to the Shift key.) and press the letter “V” on your keyboard and you get “√”. This is by far the easiest way to make a check mark although it's cheating slightly because it's actually a square root symbol.