Do NOT use Wingdings. See http://girtby.net/archives/2005/03/17/dont-use-wingdings/ for the reasons.
If you later try to copy your file to another word processor format, or try to have it viewed on a computer that does not have Windings, then your character will not come out.
This applies to any old-style symbol font, that is, a font which contains 256 characters or less and contains pictorial symbols. Unicode is what computers use now. Use Unicode symbols whenever possible and only use a symbol from Wingdings or another old-style symbol font when you have no other choice and be aware that if you do any conversion of your document you may lose the character.
The tick mark appears twice in Unicode as ✓ ( http://www.fileformat.info/info/unicode/char/2713/index.htm ) for a regular tick and ✔ ( http://www.fileformat.info/info/unicode/char/2714/index.htm ) as a bold tick. The information pages give you the decimal values for these characters which can be used with the left Alt key within Microsoft Word to produce the characters. That is, make sure that Num Lock is on, press down the left Alt key, type 10003 on the numeric keypad, then release the left Alt key. That will give you ✓. Typing 10004 will give you ✔. But you usually have to set the font to one which contains those characters. The right Alt key also works on many systems.
The tick symbol is not √ which is a square root symbol.
To find what fonts you have which contain ✓, paste ✓ into the Query box at http://www.fileformat.info/info/unicode/char/search.htm (or just type “check mark”) and mouse-press search. If more than one answer comes up, check the one which makes the most sense. Then, in that answer ( http://www.fileformat.info/info/unicode/char/2713/index.htm ), click on “Fonts that support U+2713” . This supplies a list of free fonts that contain the character: http://www.fileformat.info/info/unicode/char/2713/fontsupport.htm . You can also click on “Local Font List” and get a listing of how Unicode character 2713 appears in every Unicode font on your system. This allows you to select in a word processor, a font where it looks best to you.
WIngdings dates back to pre-Unicode days and it and other old-style Symbol fonts are still included with Windows so that old documents that used them will still show the characters. But unless you know what you are doing, NEVER use WIngdings in a new document.
Using a font in a unique proprietary coding is usually the wrong way to go.