Loose wheel nut indicator
Loose wheel nut indicators are small pointed tags, usually made of fluorescent yellow plastic, which are fixed to the lug nuts of the wheels of large vehicles. The tag rotates with the nut, and if the nut becomes loose, the point of the tag shifts noticeably out of alignment with the other tags. If too many lug nuts are loosened, the wheel can detach from the wheel stud; loose wheel nut indicators allow identification of loose nuts before this can occur.
Loose wheel nut indicators are used both by auto mechanics to identify lug nuts which require tightening, and by accident investigators to detect faults after accidents. Although not compulsory in most[clarification needed] jurisdictions, road safety bodies[who?] recommend their use, especially on large or heavy vehicles such as buses, coaches, large vans and trucks.