Let's say that we have a cardboard, a sheet of cardboard that is 20 inches by 30 inches. Let me draw the cardboard as neatly as I can. So it might look something like that. So that is my sheet of cardboard. And just to make sure we know the dimensions, it is 20 inches by 30 inches. What we're going to do is cut out the corners of this cardboard. And all the cut out corners are going to be squares.