Rozdzielczość ekranu and other 86,700 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).
This appears to be a rectangle situated vertically. There is a vertical line inside the rectangle, going from the bottom left corner of the rectangle to the top right corner. There are two small triangles, one connected to the bottom left of the line and one connected to the top right end of the line.