I am trying to create a header where the underline completely extends horizontally to the end of the document, but I cannot find out how to do this.
You can achieve a similar effect by:
- Highlighting the text
- Opening Format > Paragraph styles > Borders and shading...
- Choosing a bottom border
- Pressing Apply
If you're trying to do the same thing I was - extend the underline on the same line after some text - here's the trick:
The fix is to insert a special character. Go to Insert → Special Characters → Format & Whitespace → Whitespace, and select the ninth from the left on the top row: PUNCTUATION SPACE or U+2008. It presents a uniform space for Docs to underline. Then copy it (ctrl+c) and paste it (ctrl-v) where you need it.
Word to the wise, SAVE these instructions. I had been doing this to create headings in my resume for months, but suddenly Docs started messing up the formatting of the text. I removed the extra underlined parts and re-inserted the special characters and now it's working again.
Insert -> Special Character -> Punctuation -> Dash/Connector -> Low Line
Insert > Horizontal Line
This should do the trick.