If you're sending out menu options with your invites and need guests to return their choices to you with their RSVP, you can create a space for this on your RSVP card. If you need a little extra space, and being able to type on the reverse of the RSVP card would help, please email us at firstname.lastname@example.org so we can set up a double sided one for you.
Here's an example of an RSVP card which includes space for guests to detail their menu choices. You can make a solid line by using the underscore character on your keyboard, and then setting the character spacing to 0.0.
Instead of a solid line for your guests to write on, you might want to use square brackets instead, leaving space for them to handwrite a number.