Quotes in Custom Linetypes

I want to put the inch symbol " in my custom linetype so that I can display 18"SD for the text. Is there a way put this into the linetype definition without it reading it as the end of the text??

 

Yes. In the string portion of the linetype definition:

["string",style,S=scale,R=rotate,X=xoffset,Y=yoffset]

...use %%34, as in "78%%34STM"

Unless you have a routine where you are building these linetypes on the
fly, you might consider creating shapes to use in your linetypes instead
of text. The text in 'text custom' linetypes can vary, depending on how
the style is defined in the drawing.

Good luck.