Plate III should be laid out in the same manner as Plate II, that is, for size and border lines. In laying out the sixteen rectangles, however, the space between the center lines and rectangles must in every case be made 1/2 inch. Each rectangle is to be filled in with what is called section lining, illustrating the material of which the object is composed, and, therefore, differing accordingly. The conventions here shown are standard, and some of them will be used by the student in later work in Machine Drawing. Familiarity with them is of value to any draftsman. In drawing section lines of this character, the closeness of the lines should be governed by the area being sectioned. For large areas use a rather wide spacing; for small areas use a narrow spacing. In showing a section of any machine, the different parts are dis-tinguished by altering the slope of the section lines, whether of the same material or not.
After all the penciling of Plate III has been completed, the exercise should be inked, including the titles.