Microsoft has made a light version of it's popular Excel spreadsheet program available for free on iOS and Android devices. It has a pared down feature set so that the user does not go insane trying to dig through the options on a touch screen. One useful option from the desktop version of Excel that did not make the cut in the mobile version is the double underline.
Many number crunchers like the double underline to show that the bottom of a table of numbers is being summed.
There is still the option to use a single line border or the underline text style, but if neither of those are what you are looking for, fret not. I am here to show you a work around that will give you a double underline that will cover the entire width of the cell and resize if you change the column width. Yes my friends, prepare to have your mind blown.
Single Bottom Border and Single Underline
Shown above is the single border applied to the cells and then the underline style applied to the data. This doesn't work well as you can see because the underline only extends the width of the text. If the text does not fill up the entire column, it will never look like a double underline.
Hyphens and Single Underline
Next, you may try the single underline format and then add a bunch of hyphens. This works fine if you are never going to resize you columns. If you do resize your columns though, this technique quickly gets goofed up.
I have found two pretty solid ways of getting this done.
Two Single Underlines
The first way is to first use a single bottom border. Then, add a row and apply a single bottom border to that as well. Shrink the row height and vavoom, there you have it. One pitfall of this approach though is that the one short row that you added can trip you up later if you add data as it is still a functioning line in your spreadsheet and, if numbers get into it, you may not notice that they are there.
The final, and probably "best practice" solution is to apply the last "Titles and Headings" cell style to the totals row. This will give you a single underline above the totals and a double underline below. It makes it obvious that the row is the summation of the data and it adds a bit of color too.