Letter of rec confusion, help please!

<p>Ok so on its website, U of Chicago says that you can send in an optional letter of rec written by an additional person such as your employer. I want my boss to write a letter for me but I'm not sure how this process works...as far as I know, Common app wont let me 'invite' anyone other than a counselor or teacher to write the rec. Do I just simply ask my boss to write the letter and then mail it in with her signature on the envelope? </p>

<p>Help please? </p>

<p>thanks!</p>