1. Get a girl and do her doggy style near a wall.
2. As your about to ejaculate, smash her head into the wall inducing a nosebleed or other bleeding.
3. Continue to stamp her bloody face all across the wall, as much as possible
what animals do when they rub or place their dirty buttholes on things leaving something that resembles a stamp made our of their rear chocolate. A perfect examples are dogs who have exposed buttholes like pugs and they like to sit or lay and they move later leave a chocolate stamp behind.