When editing a Word document you may come across small black boxes or squares in the left margin when formatting symbols are displayed. It may not be possible to relocate text which includes these marks to other parts of the document. The 'black box' symbol indicates that the text has been formatted so the lines are kept together.
You can remove this formatting for any one line by clicking on any one of the black boxes. This will bring up the Paragraph dialog box. On the 'Line and Page Breaks' tab, unclick 'Keep lines together'. To remove the setting for several lines, select them all, and on the Home ribbon go into Paragraph and make the same change.