For Marcus Lemonis, the star of CNBC's "The Profit," a handshake is much more than a polite greeting.
"The best advice that I was ever given was about shaking hands and making a deal," the self-made millionaire and serial entrepreneur tells CNBC.
The advice came from his mom. "She said: 'When you shake someone's hand, you have to honor the deal that you made, and you have to do what you say you're going to do,'" Lemonis recalls.
Agreeing to something with someone has to mean something, he emphasizes — and a handshake should be enough.
"Oftentimes, people think that the only way to make a deal is to sign a legal document," Lemonis says. "But if people want to get out of the legal document, they're going to get out of it."
That's why all of his deals on "The Profit" — in which he invests his own cash into struggling businesses and tries to turn them around — are initially sealed with a handshake.
"Ultimately, I do paperwork," he explains. "But if you want to know what the movie's going to be like, watch the preview. And that's what the handshake looks like to me."