Pasek nawigacyjny dolny and other 85,000 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 icon is shaped like a rectangle with round edges. About a third of the way down there is a horizontal line running through it. In between the horizontal line and the base of the rectangle are two small circles followed by a long skinny rectangle.