To simply and accurately conduct drilling work required when a crime prevention camera is provided in a side plate of a car.

This tool is an attaching tool 9 having a rectangular shape in its top view and provided to a thin plate magnetic substance with attaching hole position designating parts 9a, 9b for designating attaching hole drilling positions to insert bracket fastening bolts, and a wiring hole drilling position designating part 9c for designating a wiring hole position to insert a wiring cable for a crime prevention camera. Since the drilling positions by a drill are instantaneously grasped by attracting electromagnetically the attaching tool 9 to a prescribed position (e.g. an upper comer part) of a side plate 2a of the car before drilling work for the attaching hole or the wiring hole, simple and accurate drilling work is carried out.