This page shows the different variations of the Sprawdź plik from an Icons8 icon pack. Feel free to resize and recolor the icon, and then download the icon in PNG format for free. Icons are available in PNG and vector.
The icon looks like a vertically oriented rectangle. however, the right corner has been folded in to form a right triangle within the rectangle. the right and bottom sides are also missing segments. instead, a checkmark shape is present in this spot