A double door where only 1 door has two handles on each side, and a door with no handles. Commonly, the inactive door (no handles) has something on the side of the door to open that door.
An acrobatic sexual act, achieved by a gentleman inserting his testicles and scrotum into a lady's vagina and having her simultaneously perform oral sex on him.
"...but Sarah, she was dirty as hell. Gave me a French Doorknob on our first nighttogether. Anyway, will the jury please deliver its verdict?"