Truck nuts

Truck nuts, also spelled truck nutz, are vehicular vanity accessories resembling a dangling scrotum. They are attached under the rear bumper or trailer hitch making them plainly visible to other vehicles behind.
History.
The "truck nuts" phenomenon existed in small numbers as custom-made scrotum sacks beginning in the 1980s. The earliest known commercial store-bought truck nuts appeared in the late 1990s but still remained a limited phenomenon. However sometime in the mid to late 2000s, their popularity surged, and truck nuts became well known throughout society even featuring on national television shows.
A number of people claim to have invented the truck nuts industry (i.e. plastic store-bought truck nuts). David Ham, owner of YourNutz.com, said he saw a pair of custom truck nuts at a rally in the 1980s, then in 1996 began manufacturing and selling plastic truck nuts commercially. John D. Sallers, owner of BullsBalls.com, says he was out driving his 4x4 off-road when someone yelled: "Go Ernie, show'em you got balls!", which inspired the idea and he began selling them in 2002. The two men sold Truck Nuts through the late 1990s and 2000s, competing both in the market and in private, exchanging angry phone calls and emails. This conflict escalated into public relations wars, social media conflicts, posts on review sites, blog attack posts, and finally leading to legal cease and desist orders. "Vice News" wrote a story about the feud called "Balls Out: The Weird Story of the Great Truck Nuts War".
Obscenity vs free speech debates.
In 2007, Maryland legislator LeRoy E. Myers Jr. proposed prohibiting motorists from "displaying anything resembling or depicting 'anatomically correct' or 'less than completely and opaquely covered' human or animal genitals, human buttocks or female breasts". He said fake testicles were "vulgar and immoral," and said his proposal was requested by an offended resident. In Virginia in 2008, Delegate Lionell Spruill proposed Bill HB 1452 to prohibit truck owners from displaying or otherwise equipping their vehicles with devices resembling human genitalia. In April 2008, the Florida Senate voted for a $60 fine for displaying truck nuts, but it did not pass the House.
In 2011, a 65-year-old South Carolina woman was ticketed by the town's police chief for obscenity displaying truck nuts on her pickup. The case, originating in Bonneau, S.C. (population approximately 480), was pending jury trial on her $445 traffic ticket. The case was continued three times and no new trial date was set. According to the Above the Law legal analysis blog, the ban was discussed in the "ABA Journal" and presented constitutional freedom of speech questions. 
The stated position of the Honolulu Police Department in 2013 from their city corporation counsel's office concerning obscene bumper stickers is, "It may be tasteless but it's protected as free speech."