His line of work is deliberately blended into the action. For instance, before telling Doris Day that their child has been kidnapped, he makes her take a sedative. Stewart's character prepares the hypodermic of sedative calmly, professionally. He's using the tools and methods familiar to him to solve the immediate problem. Characters will always use familiar tools, given the choice.
Tools are an extension of occupation, and occupation is an extension of character and theme.
A plumber with a slide rule or a nun with a machine gun seems strange. A character s choice of tools gives us insight into his or her personality and background. They are more than just props. The first morning without Mom, Hoffman has to prepare breakfast. His son wants french toast.