One person’s planets inside the wheel, the other’s around it, and a line wherever the two charts meet.
Put two charts on the same wheel and you can see where they touch: your Sun across from their Moon, their Venus beside your Mars. Each of those meetings is drawn as a line through the middle — solid where the two planets sit easily together, dashed where they pull.
It suits a couple, and just as well two best friends, a pair of siblings, a parent and a child, or two people getting married who need a present nobody else will bring.