How do you write on top of a line in Microsoft Word?

I am making a form that people will be filling out online, I need to know how you can write on top of a line. For example, "address ____________________" I need to know how to write on top of the line without the underscores moving. I knwo you can underline the underscores, but then it messes up the rest of the form when someone fills it in. Any help is appreciated!