Rustyhook is when you are fucking
doggy style, you slide your finger in the arse.
When you
pull your finger out you get a little poop on it, then you reach down with poop finger in a hook shape and thrust
your shit finger into the mouth between the teeth and cheek, then you pull your finger back hooking on to corner of the mouth like a hook.
WARNING
( THIS MUST BE DONE WITH PRECISION.)