To previously prevent an incident that a steel tower may be collapsed with a bolt (5) and a nut (6) which compose a structure such as a high-voltage transmission steel tower and fix or tighten parts and members removed by terrorism or the like.

The bolt and nut are configured so as to enclose the end of a tubular part (1) and to provide in a central part on the outside surface of the end a yellow or white, or an outstandingly colorful bulb (3) which is a luminous element such as a light emitting diode (LED) etc. at the tip of a bar pole (2) with an outstanding color and to adhesively fix one side of the bar pole (2) uprightly and to fix to cover from a hollow of one side of the tubular part (1) to the top of the bolt (5) or the nut (6) which is used on the high-voltage transmission steel tower. They prevent and compulsory suppress and arrest such terrorism that terrorists collapse the steel tower by removing the bolt and nut by means of aerial photography by a radio control helicopter.