Figure 1-11. Head and chest set.
graduations for each multiple of 10.
opaque, plastic chart with horizontal
Each 5 and 10 interval is marked
and vertical lines and a degree-
by a longer line.
azimuth scale printed in black, A re-
tractable pin at the center of the
f. Plotting Board and Rule.
degree-azimuth scale acts as a pivot
(1) Plotting board (fig. 113). The plot-
for the rule. The retractable pin can
ting board consists of two sheets of
be raised or lowered by the retracta-
plastic separated by a plywood filler;
ble pin adjustment located under the
all three are cemented together.
Metal strips are used to bind and pro-
tect the edges of the laminated board.
The top sheet consists of a white,
vinyl plastic and is 231/16 inches long,