Back Contour is the profile or grip shape of the neck. How much wood does it take to fill up your hand? Too little
equates to quicker hand fatigue. Too much is even worse, you can't reach around it. Do you play thumb over? Check out your favorite guitar and compare its neck thickness, (fingerboard face to the back of the neck), to the ones below.
NOTE: Some neck types have limited options of back contours available.