The tick or check mark symbol can be inserted into an Excel spreadsheet through the Windows Character Map tool, Symbols command on the Insert menu or its character code. The radical sign, which denotes the square root of a number, can also be used as a tick mark.
To insert the tick mark by using its character code (0252), change the font to Wingdings, press and hold the Alt key and type "0252" on the numeric keypad. The Wingdings font also offers different styles of tick marks, including ones enclosed in a box. Instead of having to be memorized, these symbols can be viewed and inserted via the Symbol command on the Insert menu.