Grace Brewster Murray Hopper (nee Murray; December 9, 1906 - January 1, 1992) was an American computer scientist and United States Navy rear admiral. One of the first programmers of the Harvard Mark I computer, she was a pioneer of computer programming who invented one of the first compiler related tools. She popularized the idea of machine-independent programming languages, which led to the development of COBOL, an early high-level programming language still in use today. Hopper had attempted to enlist in the Navy during World War II, but she was rejected by the military because she was 34 years of age and thus too old to enlist.

Throughout much of her later career, Hopper was much in demand as a speaker at various computer-related events. She was well known for her lively and irreverent speaking style, as well as a rich treasury of early war stories. She also received the nickname "Grandma COBOL".  While she was working on a Mark II Computer at a US Navy research lab in Dahlgren, Virginia in 1947, her associates discovered a moth that was stuck in a relay; the moth impeded the operation of the relay. While neither Hopper nor her crew mentioned the phrase "debugging" in their logs, the case was held as an instance of literal "debugging." For many years, the term bug had been in use in engineering. The remains of the moth can be found in the group's log book at the Smithsonian Institution's National Museum of American History in Washington, D.C.  Grace Hopper is famous for her nanoseconds visual aid. People (such as generals and admirals) used to ask her why satellite communication took so long. She started handing out pieces of wire that were just under one foot long (11.80 inches = 300 millimeters)--the distance that light travels in one nanosecond. She gave these pieces of wire the metonym "nanoseconds." She was careful to tell her audience that the length of her nanoseconds was actually the maximum speed the signals would travel in a vacuum, and that signals would travel more slowly through the actual wires that were her teaching aids. Later she used the same pieces of wire to illustrate why computers had to be small to be fast. At many of her talks and visits, she handed out "nanoseconds" to everyone in the audience, contrasting them with a coil of wire 984 feet long, representing a microsecond. Later, while giving these lectures while working for DEC, she passed out packets of pepper, calling the individual grains of ground pepper picoseconds.  Jay Elliot described Grace Hopper as appearing to be "'all Navy', but when you reach inside, you find a 'Pirate' dying to be released".

Using a quote from the above article, answer the following question: What did she use for her nanoseconds visual aid?
She started handing out pieces of wire that were just under one foot long (11.80 inches = 300 millimeters)--the distance that light travels in one nanosecond.