Understanding space is an important step in learning about design. But how, you might ask, can we see space? Think about film photography. A negative image is created from which a positive image is printed. Interestingly, those negative images, as shown in the chair image above, do a great job of emphasizing space over form.
Form and space are inextricably linked - if you change one, you change the other. Moving the location of the rail (part of the form) strongly affects the spaces of the piece. Combining drawings such as these with building full-sized mock-ups will help you to determine the dimensions of parts and position them so that spaces are in balance.