Five by Five

I have heard many Buffy fans question the meaning of the phrase, "five by five." Here are the three explanations I have come across:

1. 5 x 5 is used to indicate a square (this never made much sense to me)
2. It's a sniping term meaning the target is acquired and the shooter is ready. Supposedly this term became more widely used by cops and the military before finding it's way to tv and the general public.
3. In voice procedure (the techniques used to facilitate spoken communication over two-way radios) a station may request a report on the quality and strength of signal they are broadcasting. In the military of the NATO countries, and other organisations, the signal quality is reported on two scales; the first is for signal strength, and the second for signal clarity. Both these scales range from one to five, where one is the worst and five is the best. The listening station reports these numbers separated with the word 'by'. Five by five therefore means a signal which has excellent strength and perfect clarity - the most understandable signal possible.
   Five by five by extension has come to mean 'I understand you perfectly' in situations other than radio communication, the way Loud and Clear entered slang, post-WW2.

A combination of the first 2 is a possibility (perhaps a sniper scope is a 5 x 5 square...since I'm not a sniper, I do not know.) The third definition was found at wikipedia.

I'd love to hear any information or ideas that other people have regarding this. Especially if you're a sniper!

What am I doing here???

I just wanted somewhere to collect my thoughts and share information about Buffy which I find interesting. Perhaps others will too!

Many thanks to the "Not-So-Evil Trio" at CRZ for inspiring me to do this!