Hachures are constructed by drawing a series of parallel lines perpendicular to the direction of contours. Two forms of hachures were traditionally used in manual cartography (Yoeli 1985). In the first, known as slope hachures, the width of hachures was proportional to the steepness of the slope, thus, steeper slopes had thicker hachures and were darker. Because slope hachures generally failed to create the impression of a third dimension, shadow hachures were developed (Figure 20.1) in which an oblique light source was presumed. In this approach, the width of hachures was a function of whether the hachure was illuminated or in the shadow.