Although rarely in the limelight, American actor Robert Knapp was a dependable presence in film and on television from the early 1950s until the mid '70s. The California native began by playing small uncredited roles as elevator operators and policemen. His first supporting role came in the 1953 sci-fi film "Mesa of Lost Women." He showed up on the police procedural show "Dragnet" for several episodes and played Lieutenant Finch in the war film "Silent Raiders" in 1954. He had rare starring roles in the 1958 crime drama "Hot Car Girl" and the 1960 film "The Threat" before returning to small parts on TV in shows like "Hawaiian Eye" and the Raymond Burr classic, "Perry Mason." He was a frequent guest star on the venerable Western "Gunsmoke" throughout the '60s and on the crime drama"The F.B.I.," where he appeared in 11 episodes. His final film appearance was in the Jackie Mason crime comedy "The Stoolie" in 1972.