In the military, "click" or "klick" is a term used to denote a distance of one kilometer or 1,000 meters. It is part of the metric system and is used to communicate more information in fewer words. Soldiers may also use the term "click" when adjusting their weapons sights, as they "click in" when they adjust their weapons sights. The term probably developed because soldiers have to turn a dial that makes a clicking noise to adjust most sights. The origin of the term "klick" is uncertain, but there are a few theories that seem to have some validity to them.