nipple test
Almost better than a get out of jail free card. When you meet some slag at a bar take her home and get her naked and are not sure if her downstairs parts are tasty enough for a lick so you rub a finger down there and then rub her nipple and sneek a taste from the nipple. You can now make the decision wether or not to go downtown whithout embarassing consequences.
Oh man I should have used the nipple test last night it was like that girl was doing deep knee bends and running laps all day, sure would have saved me on mouthwash!