A sexual act between two consenting homosexuals. One man places his erect penis out and places the palm of his hand on top of the penis. Another man places his erect penis below the other man's penis with the palm of his hand underneath his own penis - both men applying pressure against the two penises. The two men then grind backwards and forwards until both ejaculate.
Hey Mark, my ass is feeling a bit sore tonight, fancy a knobjob instead?