Similar to the Dirty Sanchez. While pounding your girl(or guy, whatever your pleasure), you rub and make slow semi-circles around her asshole and the without warning you JAM your finger in her ass. When she turns around to yell HEY!! you give the ole' fish-hook. The shit on your finger resembling rust on a hook. You can go for the Double Rusty Fish-hook, but you need to stick another finger in your own ass right before you jam it in her and then WHAM-O!
Dude, I was railing the chick the other night and she was moaning so damn loud that I had to give her the rusty fish-hook just to get her to shut up...
Derogatory sex position: The act of sticking a finger in the butt of a women during doggy sex,reaching for her face and hooking her mouth like a fish. Possibly originating from a man obsessed with fishing.
"I gave it to her from behind and before she could notice, I gave her the old rusty fish-hook..."