Placing the dog on a table facing your left, Place your right hand over the wither, and feel for the scapular spine that runs down the length of the shoulder blade.  Place your index finger along the axis of this spine, and point your middle finger straight down (vertically).  Now look at the angle between your index and middle fingers.  This is the complementary angle of the shoulder blade. In a well angulated dog this will be about 30 degrees.  (The correct shoulder blade angulation should be 60 degrees relative to the horizontal or 30 degrees relative to the vertical.) (30 + 60 = 90)