Using submission techniques on your partner during sex. Screw-jitsu is frequently employed to facilitate unhindered getaway after sex, to spice things up, or just for practicing techniques.
Brian: Where's your wife?
Scott: Sleeping upstairs.
Brian: During your party?
Scott: She was giving me birthday head and I put her in a triangle. Maybe I should have let up before she went out. She didn't tap out...
Brian: Well she should know the rules of screw-jitsu by now.