That's called the quart of blood technique. Do that, a quart of blood would drop out of a person's body.
7 seconds sound clip from the Trading places (1983) movie soundboard.
You can hear this line at 00:23:53 in the Blu-ray version of the movie.
Quote context
[...]
- I ain't cut him with no knife, man.
- But you told me last night you cut the dude.
- It's with these I cut him. I am a chain belt in Kung Fu. Bruce Lee was my teacher. Watch this.
- Tell him how you beat on the cop.
- It were no cop, man. It was cops, plural. Nine or ten cops...
- Beat the shit out of ten cops, man, and had to change my whole strategy around.
- Yo! When they brought you in here and booked you, you was crying like a pussy.
- Yeah.
[...]