Let A C - about 3 3/4 inches long - be a given line. Suppose it is desired to divide it into 7 equal parts. First draw the line A J at least 4 inches long, forming any convenient angle with A C. On A J lay off, by means of the dividers or scale, points D, E, F, G, etc., each 1/2 inch apart. (If dividers are used, the spaces need not be exactly 1/2 inch.) Draw the line J C and through the points D, E, F, G, etc., draw lines parallel to J C. These parallels will divide the line A C into 7 equal parts.
If a series of parallel lines, cutting two straight lines, intercept equal distances on one of these lines, they also intercept equal distances on the other.