Ma'anar ƙamus na "misali ma'auni" ƙayyadaddun ma'auni ne don faɗin hanyoyin layin dogo, wanda ya kai ƙafa 4, inci 8.5 (milimita 1,435). Wannan shi ne ma'aunin da aka fi amfani da shi don hanyoyin layin dogo a duk duniya, kuma yana ba da damar tafiyar da jiragen ƙasa cikin sauƙi da inganci a yankuna da ƙasashe daban-daban. An fara fara amfani da ma'aunin ma'auni a Biritaniya a cikin ƙarni na 19 kuma tun daga lokacin an karɓi shi azaman ƙa'idar sufurin jirgin ƙasa ta duniya.