The familar sexual position where the man stands and the woman kneels in front of him and gives him head. She is in the Girl Guide position.
As most women know and use this position, the story is that they were all taught it in the Girl Guides. In some versions, all Guides learn it routinely. In other versions the Guide is taught it in order to obtain her fellatrix attainment badge.
Of course these stories are untrue. There is no such thing as a Guide fellatrix badge. And all Girl Guides are fine, morally upstanding young women.
Jane: how do you want me? Is on my knees OK?
John: Yeh. The good old Girl Guide position is fine.
(a little later . . .)
John: That was great . . . obviously you got your fellatrix badge when you were in the Guides.