The cleaning lady with the mop
A mop was a tool used to clean up spilled liquids or dust from a flat surface such as a floor.
In 2364, upon entering the Dixon Hill holoprogram, Jean-Luc Picard encountered a woman mopping the floor just outside the private investigator's office. (TNG: "The Big Goodbye")
A mop leaned against the wall in a Dilmerian prison where Beckett Mariner was jailed. (LD: "Fully Dilated")