Evaluating structure on eight week old puppies using lines
These are the two lines needed to evaluate the front structure and angulation. The first runs from the point of the shoulder (not the keel) to the back of the shoulder blades, or whithers. This is the shoulder layback, and impacts reach and drive and length of neck. The second runs from the point of the shoulder to the elbow. That is the upper arm.
This is how you evaluate front angulation: draw a line from the back of the shoulder blade right down to the foot. If there i good layback of shoulder and good length of upper arm the foot will be well underneath the body. If the front leg is directly under the ear you know the upper arm is short.
The rear angulation is determined by drawing a line from the point of buttocks straight down, Where it dissects the foot (toe vs heel) is how much angulation is in the rear.
Drawing a line straight across the topline helps determine shoulder layback and length of neck. None of the head should be below the topline. (While it appears this puppy has a sloping topline, I have found those with lots of front angulation tend to lean forward and make their toplines slope, but are normal as adults.)
To determine body length vs. leg length, draw a square from the elbow to the point of stifle, down to the ground and back across. Get in the habit of drawing this square on every dog you see, and every puppy you evaluate. Many are long bodied/short legged, being much more of a rectangle than square.
The same puppy at seven months. Structure is accurate from what it was at eight weeks.