Link and Pin

A Sexual act in which one person backs or walks into another and you have to get the dick in without crushing your fingers, much like that used to couple train cars together.

I like to begin sex with the ol' link and pin.

Second Diddle

A man who allows another man to sleep with his significant other, provided that he is allowed to watch and masturbate.
A cuck who wants to feel included.

It was hard to have sex with my best friend's wife because he was playing Second Diddle.