Where you extend your big toe and tap upon the girls anus (as if to knock). The girl then spreads her ass cheeks and you proceed to stick your entire foot in the girls anal canal while singing the Doors classic tune Break On Through. Must be done on the first date to essentially just "get your foot in the door"
Steven: So why do you wish to work here at Rubys?
Ralph: I've always wanted to work for in a restaurant now I'm just trying to get my foot in the door.
Lee: How'd the first date go?
Dan: I got The Foot In The Door
Lee: *High Five*
Dan: What happened to your thumb?