These are objects that you can draw in 3 point perspective. 3 point perspective is when you have 3 vanishing points, one on the left, one on the right, and then one in the middle top or middle bottom. Then you draw this box to estimate/map out how big or small the object will be. You then go on to draw the object. This was challenging and it took alot of time especially for when you do elipsis and such. You need to learn 1 point and 2 point perspective first to know how to do this.