The AutoFormat As You Type tab of the AutoCorrect dialog box. Make sure the AutoFormat As You Type tab is selected.Word displays the AutoCorrect dialog box. Click Proofing at the left side of the dialog box.In Word 2010 and later versions display the File tab of the ribbon and then click Options.) (In Word 2007 click the Office button and then click Word Options. This feature of Word is controlled by following these steps: This is not the only three characters that result in this type of replacement-characters for lines-but if you don't know the source of the line, it can be frustrating. For instance, if you type three underlines on a new line, and then press Enter, you get a solid line that extends the width of your document. One such liberty is the adding of borders to paragraphs based on what you type. Word, by default, takes some liberties with what you type.