Write an article based on this summary:

Click Show/Hide ¶. Press the TAB key as many times as you want. Select the tab characters that you want to underline. Press CTRL+U to apply a simple underline format. Click the font tab for other options. Insert table cells with a border for online documents.
This should be found in the Home tab, in the Paragraph group. Doing this allows you to see the marks that indicate spaces and tab stops, so you can underline the proper amount of space. If you want to print the document, these markings will not appear. Create the amount of space you want to underline by tabbing over as many times as is appropriate. After you've created the space, highlight the tabbed space as you would normal text. All you need to do is use this hotkey combination, or follow the steps in the previous section to highlight the empty space. To apply a different style of underline, like the double or the other decorative styles, click on the Home tab, then select the Font Dialog Box Launcher and select Underline style to choose a different underline style. If you're editing an online document, start by clicking the space you want the line to be. Then, click on Insert and select "Table."  Click the upper-left box, which should allow you to insert a 1x1 Table. Make it a 2x1 Table if you want any intro text or other content before the underline. Move the pointer over the end of the table to change the length of the line, then select the table by right-clicking, and click Borders and Shading, and then click the Borders tab. Under Setting, select None. Under Style, click the line type, color, and width of the underline that you want in the document.