performance or, if they get sidetracked on another topic, to get them focused back on the case. DiNozzo is usually the recipient, due to his outlandish behavior and offensive remarks. His team members occasionally slap one another in this way, but none of them apply it to Gibbs for fear of retribution. "Hiatus" (season 4) reveals that Gibbs acquired the habit from Mike Franks, who occasionally did it to Gibbs when he was in charge of the team. The only people Gibbs does not slap in his work circle are his superiors, including NCIS Directors Jenny Shepard and Leon Vance; Abby Sciuto, whom he regards like a daughter; and Dr. Donald Mallard, a longtime respected friend. On one occasion (Season 3's "Family Secrets"), Gibbs slaps himself for covering up evidence of an organ transplant. Another of Gibbs' quirks is his tendency to stop the building's elevator between floors if he needs to have a short, urgent, private conversation with someone. He does this most often with his agents, and occasionally with his superiors or other law enforcement personnel. He also used it in several episodes for conversations with FBI agent Tobias Fornell, who joked that it was their favorite conference room. In the Season 13 two-part story "Sister City", Gibbs and Dwayne Cassius Pride (an NCIS agent stationed in New Orleans) have a disagreement over which of them stole this idea from the other. In the episode "Faking It", it is revealed that Gibbs speaks fluent Russian, and he at least speaks a little Japanese and Chinese ("Call of Silence" and "My Other Left Foot", respectively). He also signs American Sign Language, which appears in many episodes in conversations with forensic scientist Abby Sciuto, whose parents are deaf. Gibbs follows (and occasionally breaks or revises) a long series of rules, which he appears to have memorized, that apply to life situations and casework, and are a frequent episode plot device. These include "never go anywhere without a knife". His team is known to quote them by heart after learning them via osmosis from working around him. There was no evidence that the rules existed in writing prior to Season 7 (Episode 24 "Rule 51"), when Gibbs opened a small metal box and added rule 51 by writing it on the back of the slip for rule 13. Most of the rules are recited in Season 12 Episode 10 "House Rules"