Crossing two of your fingers when fingering a chick. Hypothetically, any two fingers can be used, but using the third and fourth fingers with the third pointing up usually gets the best results.
Big L: I gave that ho the southern cross, and she screamed.
Nerd: Ah, yes. I am acquainted with the man who invented the Southern Cross. I believe it works by stimulating the G-spot continuously. But never having used it myself, I find myself a bit out of my element.