Clenching the Wrench

When you aggressively stroke your cock so hard you shit yourself. This may cause small lacerations along the shaft/tip, and or severe fright from masturbation.

Friend: "Is Tommy here?"
Mom: "Yes, he's upstairs in his room"
Friend: "Okay" *goes to walk upstairs*
Mom: "I wouldn't go up there unless you want to watch/hear him clenching the wrench. He's been doing it all week."