In the US, the end of every train is now indicated by a bright red light called (officially) an End-Of-Train Indicator. Unofficially, it's called a FRED -- for F*****g Rear End Device (and no, the word is not "flashing"; one of the guys who worked to create it told me what it means).

Would such a thong be a FFED -- or F*****g Front End Device? Will you be able to glimpse the light between the...nevermind. Forget I mentioned it.