Creating Custom Symbols In The Symbols Library File

The symbols library file contains the symbols that SolidWorks uses. By default, the symbol library file is located in C:\ProgramData\SOLIDWORKS\SOLIDWORKS XXXX\lang\english\gtol.sym

To create a custom symbol, open up the gtol.sym file in notepad.  The syntax to create a new symbol can be found at the top of the file.  It has been copied below as well:

-------------------------------------------------------------------------------

;; Format:
;;
;; #<Name of library>,<Description of library>
;; *<Name of symbol>,<Description of symbol>
;; A,LINE xStart,yStart,xEnd,yEnd
;; A,CIRCLE xCenter,yCenter,radius
;; A,ARC xCenter,yCenter,radius,startAngle,endAngle
;; A,SARC xCenter,yCenter,radius,startAngle,endAngle
;; A,TEXT xLowerLeft,yLowerLeft,<letter(s)>
;; A,POLY x1,y1,x2,y2,x3,y3
;; A,BOUND x1,x2
;;
;; Units:
;;
;; All x, y, and radius values are in the symbols grid space (0.0 to 1.0),
;; where 0,0 is the lower left corner and 1,1 is the upper right corner.
;; The grid space is considered to be the height of a character squared.
;; All angle values are in degrees.

-------------------------------------------------------------------------------

Note that if a custom symbol is used in a file, anyone who opens the file without the symbols library file will only see the syntax.  One common example of this is when SolidWorks is upgraded and instead of a diameter symbol, they see the following:

"<MOD-DIAM>"

This syntax references the "MOD" library and the "DIAM" symbol within that library.  If a symbol exists there, then it will replace the syntax.  Otherwise, only the syntax will appear.

If syntax is showing up instead of the expected symbol, please refer to the article Drawing Dimension Does Not Display Any Dimension Symbols