Craig Toomy: Oh I'm real scared now.
Nick Hopewell: Do you ever watch Mr. Spock on Star Trek?
Craig Toomy: What the hell are you talking about?
Nick Hopewell: Because if you don't shut your cakehole, you bloody idiot, I'll be happy to demonstrate his Vulcan sleeper-hold for you.
Answer: In the book he slaps her across the face during a heated argument. I can only assume that is what he is talking about.