In a

very simple way you can make a mechanical aid to help you draw and visualize perspective accurately. Take a box, remove the bottom, and divide the open end into squares by criss-cross threads, as illustrated. Set up this frame in front of the subject to be drawn and note how the squares divide the picture. Draw squares on your paper, and copy what you see through each square in the box. You will find that you have drawn objects in perspective. That is, you have drawn what your eyes tell you exists, and not what your mind knows exists.
A square-paned window provides a framework of vertical and horizontal lines which helps to determine the angle of the perspective lines.