What's left behind when someone defecates in a hard-to-reach public space without cleaning it up.
Y'know that giant shoe sculpture in the south wing of the mall by the Nordstrom? Someone left a San Francisco Business Card in it and it's really fouling up that whole hallway.
When presenting TWO business cards to a woman- or member of the opposite sex- this means that that person is interested in a relationship with the receiver of the cards- and that the intention is to reach 3rd base by the end of the first date... however this is at the discretion of the receiver.
I gave her 2 business cardflirtations so that she would know I was interested in her.