A removable locking system for a fluorescent U-tube electrically connected to a mounting body connected to a surface. The mounting body has a flange extending over the coupling member of the connecting end of the U-tube at the mounting body. A locking screw member is threaded through a hole in the flange into pressing contact with the top of the coupling member of the U-tube. A self-locking washer is positioned between the head element of the screw and the top surface of the flange. The locking screw can be rotated to lock or free the U-tube from its mounted association with the mounting body.