Fig. 6
Fig. 7
Figure 6 illustrates the method of drawing vertical and horizontal lines, the same method being applied lines parallel or perpendicular to a given line at any angle. Place either triangle with its right angle in the position of point B, and its edge AB lying along the lower guide line (or the upper guide line could be used). Place the other triangle against the first one (usually the longest side is used and hold it securely down against the paper with the left hand; then with the right hand slide the first triangle to the positions desired to draw horizontal lines along the edge AB as at DE, or to draw vertical lines along the edge BC as at HI. This method can be used for laying out the guide lines themselves. In that case the longest edge of the 30° triangle is preferred in the position of AB.
Figure 7 illustrates the method of bisecting a space. Lay the triangles in the positions indicated to find the center point of the letter A, for instance. With the one triangle in the dotted position draw line BB',through point B, and in the position shown in solid lines draw line AA' through point A. Then by turning the triangle draw line CD vertically through the intersection of lines AA' and BB'. This line marks the midpoint for drawing—between A and B.
7
