The problem of fixing to ledges is the swing of the door, if fixing directly to the ledge. Most commonly rather more decorative hinges are fixed to the face side in alignment to those ledges. In my house I have replaced all of the original pine ledged and braced doors (1920 house). The hinges are placed under the ledges! These doors though pine, are incredibly heavy a struggle for a one man lift! Though it seems like sacrilige to replace them, they were stained originally and then decades of paint layers. To remove hinges I would have to remove ledges first, which are clench nailed. The best set up is a framed ledged and braced door using butt hinges.