US Patent 6915585 Spirit level

A spirit level including first and second profile elements which can be displaced relative to one another in a telescopic manner and fixed relative to one another by means of a fixing element. In order to ensure that the first and second profile elements remain aligned with each other irrespective of their position, the first profile element is a hollow profile consisting of two sections which can be joined by means of the second profile element. The first section is joined to the second profile element and the second section can be moved along the remaining area of the second profile element. When the second profile element is at least partially uncovered by the second section, the second profile element can be subjected to the action of force in the direction of a profile wall of the second section of the first profile element.