After the building has been laid out, and the batter boards are in place, the next work which a carpenter is called upon to do is the framing. This consists in preparing a skeleton, as we may say, upon which a more or less ornamental covering is to be placed. Just as the skeleton is the most essential part of the human body, so is the frame the most essential part of a wood building; and upon the strength of this frame depends the strength and durability of the structure. When the carpenter comes to the work, he finds everything prepared for him; the cellar has been dug and the foundation walls and the underpinning have been built. It is his business to raise the framework on them. First is the wall, then the floors, and then the roof. Therefore, the subject may be subdivided, and considered under these three main headings. In connection with the walls we may consider the partitions as well as the outside walls, and in connection with the floors we may consider the stairs, while the roof may be taken as comprising the main roof and also subordinate roofs over piazzas, balconies, and ells. This covers all the framing that will be found in a wood building, except special framing. (See page 147, Part III.) Whatever framing there is in a brick or stone building is similar to that in a wood building, with the slight differences which may be noted as we come to them.