Finger rule 

A rule for determining a woman's worth during a hookup. One finger is a gift from above, two fingers is a perfect fit, three or more and you've got a whore.

"The finger rule lets me know that this girl was a gift from above, I could barely fit one finger in there"

Finger rule by HawaiianHigh August 21, 2008

3 Finger Rule

if you can finger a girl with 3 fingers, you should do her at your place that night.

Jon: Let's see if the 3 finger rule applies to Stacy.Can i finger you Stacy?
Stacy: Yes Jon.
Jon: Well meet me at my place around 9ish, you passed the 3 finger rule.

3 Finger Rule by Pat da Baker n' Ian May 6, 2009

The finger rule 

The rule is a game, were you have to make an OK sign with your hands below the waist; If someone sees it then you can do one punch to them. If the person who sees it puts their finger in the hand and gets it out without being caught, they get to punch you 5 times.

billy used the finger rule on his friend, but his friend quickly put his finger inside. Billy got punched five times.

The finger rule by ULTIMATERIZUUMANN January 22, 2018