The Wonderful World of Withdrawal
Coitus interruptus, otherwise known as withdrawal, is a method of birth control in which a man, during intercourse, "removes the hotdog from the microwave". Or "sails the ship out of the bay". Or "pulls out". He then deposits his "crew" somewhere far off, perhaps in a tissue. That way his "crew" gets nowhere near the "pirate's treasure", if you will.
Withdrawal provides protection forever until the next time you "do" it, provided that you withdrawal correctly. It won't work if you mess it up. It stops every stage of fertilization, because it makes it impossible for the stages to begin. Withdrawal is used by the male; the female may be able to do something similar, but it would be uncomfortable and she would need plenty of wiggle room.
Side effects of withdrawal include messiness. That's pretty much it. Withdrawal does not protect against STDs. According to bedsider.org, typical use of withdrawal gives a 78% chance of preventing pregnancy. Perfect use of withdrawal grants a 96% chance of preventing pregnancy. Astounding!
^Gene Wilder, seen here "exiting the tunnel"