With apologies to all those who tried to help, perhaps we assumed incorrectly that there was a standard graphic used to illustrate rigid insulation. In Canada, rigid insulation is typically drawn by a rectangle of dimensions equal to the insulation material thickness and length in section, filled with a repeating pattern of short lines (perpendicular to the long axis) which are 2/3rds the width of the rectangle, alternating in direction, and staggered equally along the length of the section.