Throughout his nearly 20-year tenure on NCIS, Mark Harmon’s character Leroy Jethro Gibbs lived by a strict set of personal rules. Recently, Mark Harmon Gibbs rule knife—and it’s one that proves both practical and useful in everyday life.
The Iconic Gibbs Rules on NCIS
Gibbs’ rules became a cornerstone of the CBS procedural series, captivating audiences for 18 full seasons and beyond. Following his debut in the JAG two-parter “Ice Queen” and “Meltdown,” Harmon brought the character to life with remarkable depth. Over the show’s run, viewers discovered dozens of rules that Gibbs lived by, each reflecting his disciplined Marine background and NCIS experience.
Rule 9: Carry a Knife—Harmon’s Top Pick
During an appearance on the Partners & Probies podcast alongside longtime NCIS technical advisor Leon Carroll Jr., Harmon was asked by fans which Gibbs rule stood out to him most. The actor didn’t hesitate to share his answer, even pulling out a pocket knife to demonstrate:
“Rule 9, carry a knife is a good one. You’d be surprised how useful it is. All the boys, they all carry a little pocket knife, and you can forget this sometimes, and you’re getting on an airplane, and then they take your little pocket knife, and it’s gone. But it’s just a handy tool.”
Why Carrying a Knife Is More Than Just Self-Defense
Harmon emphasized that carrying a knife isn’t necessarily about defense. Instead, it’s a practical tool that serves multiple purposes. A pocket knife can be invaluable for:
- Cutting rope, string, or thread
- Opening packages or containers
- Using the mini-scissors for delicate tasks
- Helping others who need a blade in the moment
- General utility purposes in everyday situations
As Harmon noted, “oftentimes people are saying, ‘Anybody got a knife?'” This universal need demonstrates why Gibbs’ Rule 9 resonates as practical wisdom.
Gibbs’ Use of Knives in NCIS
For Gibbs specifically, a knife held even greater importance. As a former Marine and NCIS Special Agent, the character often relied on various blades for tactical purposes—cutting tires during investigations or engaging in combat situations. His need for a knife extended beyond everyday utility to professional necessity.
From NCIS Agent to Alaska’s Remote Living
After officially departing the NCIS agency in Season 18, Gibbs’ character chose a quieter life in Naktok Bay, Alaska. Following his final mission with Timothy McGee and Alden Parker in “Great Wide Open,” he settled into remote living—a lifestyle where having a reliable knife becomes even more essential for survival and practical needs.
Mark Harmon’s Continued Role in NCIS Universe
Though Harmon hasn’t reprised Gibbs on the main NCIS series since 2021, he remains connected to the franchise through NCIS: Origins. In the prequel series, Harmon serves as executive producer and narrator, voicing the older version of Gibbs while Austin Stowell portrays the younger agent. Harmon has also made two on-camera appearances as Gibbs in the prequel—once in the pilot and again in the Season 2 episode “Funny How Time Slips Away.”
What’s Next for NCIS: Origins
NCIS: Origins Season 3 is scheduled for CBS’s 2026-2027 TV schedule, though with a reduced episode count compared to previous seasons. With 10 episodes planned, fans hope that upcoming installments may explore why carrying a knife became such an essential part of Gibbs’ philosophy and daily life.