When Larry's wife Lori puts all four of her knuckles in between Larry's asscheeks during sex. The asschecks being the bread and knuckles being the meat.
Lori gave Larry the knuckle sandwich combo last night after he forgot her birthday.
After dropping a load in a woman's mouth, make her spit it out into your hand, then slap the shit out of her with it.
When Beth kept complaining about being hungry, I fed her a knuckle sandwich with extra mayonnaise and it took care of both the hunger and the complaining.