Used by a group of weed smokers when there is only a small amount/only one joint left.
Implys taking two tokes in quick succession, much like an M16 machine gun fires bullets. The doob is then passed on quickly to the next victim.
Marc fell to his knees after participating in two RF
Gary: "Its two RF!! Why have you taken eight draws?!?"
Ian: "Nah man, this is only my second draw."