While performing intercourse "doggie-style" this maneuver involves the pitcher inserting his curled finger
into the catcher's mouth and pulling back to degrade the subject or cause pain.
A "double fish hook" involves the same maneuver using both fingers.
A "rusty fish hook" involves fingering the ass of the catcher prior to insertion of the finger
(s) into the mouth.
When I walked in I saw Carlos spanking your sister's ass and giving her the fish hook.