Knock sacks 

To knock sacks is to slam you and a bros nutsacks together while you are doing double penetration on a girl.

Bro, me and Johnny are gonna knock sacks on Alyssa tonight.

Knock sacks by Willy the Huge October 4, 2017

knock-kneed, hammered-down, hollow-chested, smelly sack of Siberian sheep shit 

a loser or piece of shit individual; a tool or undeniable goof.

I have absolutely no respect for that knock-kneed, hammered-down, hollow-chested, smelly sack of Siberian sheep shit...what a scumbag!

knock-kneed, hammered-down, hollow-chested, smelly sack of Siberian sheep shit by weave March 24, 2003

Knack Sacker 

A person with the ability to hit another with their scrotum without the other's notice. Usually done by people who have had little to no sexual intercourse in at least four years.

Man did you see that? When the woman wasn't looking, Roberto opened his pants and gently struck her leg with his testicles. What a Knack Sacker.

Knack Sacker by Adolf-Alias Huxley June 3, 2010