ng, which saves making a
second view.

[Illustration: Fig. 120.]

[Illustration: Fig. 121.]

[Illustration: Fig. 122.]

[Illustration: Fig. 123.]

It would appear that under some conditions this might lead to error; as,
for example, take the piece in Figure 123, and there is nothing to
denote which is the length and which is the diameter of the piece, but
there is a certain amount of custom in such cases than will usually
determine this point; thus, the piece will be given a name, as pin or
disk, the one denoting that its diameter is less than its length, and
the other that its diameter is greater than its length. In the absence
of any such name, it would be in practice assumed that it was a pin and
not a disk; because, if it were a disk, it would either be named or
shaded, or a second view given to show its unusual form, the disk being
a more unusual form than the pin-form in mechanical structures. As an
example of the use of the cross to denote a square, we have Figure 124,
which represents a piece having a hexagon head, section _a_, _a'_, that
is rectangular, a collar _b_, a square part _c_, and a round stem _d_.
Here it will be noted that it is the rectangular part _a_, _a'_, that
renders necessary two views, and that in the absence of the cross, yet
another view would be necessary to show that part _c_ is square.

[Illustration: Fig. 124.]

[Illustration: Fig. 125.]

A rectangular piece always requires two views and sometimes three. In
Figure 125, for example, is a piece that would require a side view to
show the length and breadth, and an edge view to show the thickness.
Suppose the piece to be wedge-shaped in any direction; then another view
will be necessary, as is shown in Figs. 126 and 127. In the former the
wedge or taper is in the direction of its length, while in the latter it
is in the direction of its thickness. Outline views, however, will not
in some cases show the form of the figure, however many views be
presented. An example of this is given in Figure 128, which represents a
ring having a hexagon cross section. A sectional edge view is here
necessary in order to show the hexagonal form. Another example of this
kind, which occurs more frequently in practice, is a cupped ring such as
shown in Figure 129.

[Illustration: Fig. 126.]

[Illustration: Fig. 127.]

[Illustration: Fig. 128.]

[Illustration: Fig. 129.]

EXAMPLES.

Let it be required to draw a rectangular piece such as is s