To improve safety of equipment such as a bicycle by visualizing fastening status of a quick release and a bolt with a knob.

By fastening the quick release 1 and the bolt 2 with the knob through a spring hole 12 and a base hole 13, the spring 6 is bent, a green display part 4 goes up by fulcrum action of a protrusion 7 of a base 5 and covers a red display part 3. Color change from red to green occurs when sufficiently fastened can be visually recognized from three directions by making a part of a case 16 for covering from these display parts to the protrusion 7 part transparent or as an observation hole.