Have you ever needed a OHM symbol (Ω) on a drawing? Perhaps you need a registered Trade Mark, Copyright symbol, or other Greek letters commonly used in equations or electronics? When generating a drawing note, it may be necessary to use a symbol that is not available in the standard SolidWorks ’Symbols’ library. This valuable tip immediately expands your Symbol library, all without you having to manually sketch a symbol, make a block, and so on.
There is a good old Windows System Tool called the Character Map. This handy program allows you to find and copy symbols for use in your annotations such as drawing notes or file properties. 
You can locate this program in Start>All Programs>Accessories>System Tools>Character Map.
Simply browse to find the symbol you want to use and click on the ‘Select’ button and then click on the ‘Copy’ button. This places it onto your clipboard. And as you guessed it, proceed into SolidWorks and paste it into your notes.
In addition you can find the OHM Symbol from the Fonts SWGrekc or SWGreks with the capital letter “W”. Just for fun you can check out wingdings in the Character Map tool to see all the symbols at once that could also be used.
