"The first view is called the front view. Now, suppose I change the top view to this c; thickness is shown here, and if I say, make two of these out of white pine, you would know all that would be necessary to go ahead.
"Again, suppose I give you this sketch a ([Fig. 24]), and ask you to make two out of gum wood. You would be completely at sea, because that front view might have any one of these top views shown at b, c, d, e ([Fig. 24]). In other words, it might be a triangle without thickness, a wedge, cone, or pyramid.
Fig. 25. Three views of a book
"So you see, two views are absolutely necessary, and very often a third, taken from the right or left side. The three views of a book would look like [Fig. 25]. The side view is not necessary in this case, but that is the way it would be drawn if a third were needed. You will have plenty of opportunities for practising this as we get along with our tool work, because in order to understand drawings you must be able to make them. Suppose you try your hand now, by drawing the two views of a cylinder, two inches in diameter and three inches high."
Ralph rolled a sheet of paper up until the ends met, to illustrate a cylinder, and the drawing produced by Harry looked like a. ([Fig. 26].)
Fig. 26. Mechanical drawings of cylinder and cone