Hi plupi, your drawing seems very good to me. Some things that I noticed: The contour lines that wrap around something to show its form are perpendicular to the long axis. For example, if we have a cylinder, the contour lines of this cylinder will be perpendicular to the line that crosses through the center of this cylinder. In the ulna and radius in your drawing, I see some contour lines that are not in the right perspective ( I think that if you erase the shadow and think of those bones as simpler shapes, it will be easier to find how to draw the contour lines). If we draw the whole humerus as a cylinder, then all the contour lines that wrap around it will be similar, because there won't be any plane changes and the contour lines will be perpendicular to the cylinder's long axis, but in your drawing they are all different (remember that we don't draw the contour lines of the actual shape of the bones, but the simplified version of them, in this case a cylinder). Try to draw the spine of the scapula like little boxes, without curves, because it will help you see the plane changes and understand how to draw the contour lines. Lastly, you forgot to add width to the acromion process of the scapula (above the sphere, indicating the humeral head). Keep up the good work :)