Linijka and other 86,400 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
The ruler icon is a rectangular shape icon with lines on onside. There are four smaller lines, which represents centimeters. There are also three longer lines that are about double the length of the centimeter lines and the longer line represents inches.