Hiii,
im really new to drawing, been drawing for like 4 months now? im learning anatomy and i want to REALLY use squares and 3d shapes but i actually cant understand how people use it when studying the human body.
I sent a drawing I did today and the anatomy breakdown I drew, but looking online I keep seeing people use squares and like triangles to simulate the ribcage and all the other stuff. I want to understand it like I was able to understand the shapes of a human face. I might be super confusing but i sent some pictures of what im talking about !
Like in a way i just wanted to know how others understood it or like how i should think of it ! 
Also critique of my work is SUPER welcome!!!