What does "nuts and bolts" mean in gay sex?

What is nuts and bolts?

Slang reference for the male genitalia, meaning the penis and scrotum.

Definition

Nuts refers more to the testes within the scrotum, while the bolt portion of this slang term, refers to the Penis itself. This is due to its shape resembling a bolt, long and circular, with a top like a bolt has. Nuts because they are located at the end of the bolt, which the balls are.