Pudełko kartonowe and other 84,100 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).
A cardboard box is a bunch of rectangles that combine together folding it to mold it as one to make it into a container. On the sides there are small slits that have a handle to grasp it on, these are lines that come to a point in the top-middle of the side rectangles.