Mark Harmon, who portrayed Leroy Jethro Gibbs on NCIS for 19 seasons, has identified the character's rule he follows in daily life. The actor discussed the topic during a recent appearance on the official NCIS podcast.
Harmon joined current cast members Brian Dietzen and Diona Reasonover on the NCIS: Partners & Probies podcast earlier this month. He selected Rule 9, which states never go anywhere without a knife, and demonstrated by pulling a Swiss army knife from his pocket. Harmon described the item as a handy tool that proves useful in many situations.