A: Can you go get me some all-natural deodorant?

    B: All-natural deodorant? Deodorants with chemicals in them work much better.

    A: No way! All the chemicals are bad for your health. I don’t want to get cancer.

    B: Yeah, but I don’t want to have a girlfriend who smells bad. You can buy all-natural food, but I draw the line at personal hygiene.

    Note: This idiom means to “impose a restriction or limit.” It invokes the image of drawing an actual line and telling someone that they cannot cross the line.