what is a click

[glenis]

in american war films ,especially those set in vietnam ,you here directions given as 2 clicks west 4 clicks to the south -what exactly is a click ?

[Mortartube]

A click is a slang term for a kilometre

[Quizmonster]

The word is military slang for 'kilometre', as Mortar says. It most probably came from the movement of the odometer, calibrated in kilometres rather than miles in some military vehicles. In other words, at the end of each kilometre travelled, the gauge would 'click' over to the next number. The number of clicks, therefore, equalled the number of kilometres, so the word was transformed to take on the new meaning.

[glenis]

many thanks to you both