Abstract: A combination of bi-directional levels is provided as an integral part of the projecting terminal section of a very thin rule. Assembly within the rule section is accomplished by means of over-sized apertures to receive centrally disposed therein fluid level cylinders with a casting of transparent hardened moldable base material encompassing the rule, and interstitially surrounding said levels such as to form a capsular structure maintaining the rule in proper spaced relation for folding, in the instance of a folding rule, with a structural reinforcement for the section of rule supporting the levels.