So if you still ask yourself what is the square jaw type... Have a look at the typical model's face of Agostina Bettinelli.
Notice how sharp, jutting are her great facial features.
Over developped chin, cheekbones, jawline and angle are characteristics of the model face and for good reason: these kind of facial structure are corollary of efficient mechanical structures which we are genetically predisposed to find 'beautiful'.

Agostina is a very beautiful, feminine woman with an A grade Chin, B+ jaw angle and flat jawline.