underlining in word 2007?

I am trying to create a line in word that I can type on and it will not break. There are some already there because i am using a document started by someone else. The only way I know to make a line is to shift and use the - key. But when you type on it it breaks. I can't just underline the info I type because I want the line to extend beyond my type for a few spaces. Thanks for your help.