by using the pencil or ink and a plastic rule. Fill in the bar lines
by using the pencil or ink and a plastic rule. Fill in the bar values
with the plastic tape or adhesive sheeting cut to the required lengths
with a razor blade.
Figure 12. Bar graph made with adhesive sheeting
21. Flannel Board
Mount a gray-felt or flannel-covered board in place of the projec-
tion screen. Project a basic image on the board, and add the required
flannel-board symbols. By this method, it is not necessary to super-
impose elements on the flannel and the added symbols are spotlighted.
Make a partial drawing on carbon-coated film on the projection
stage. P r o j e c t the part drawing on a blackboard. and then com-
plete it on the blackboard in chalk. In this way, many variations
of the projected basic construction can be worked out without destroy;
ing the orginal drawing.
To demonstrate the physical properties or chemical reactions of