What do tick marks on contour lines indicate for a fill?

Tick marks on contour lines, also known as hachures, indicate a change in elevation on a topographic map. Specifically, they point toward lower ground. This is an important feature in land navigation because they help map users quickly identify the direction of steep slopes or valleys. When you see these tick marks on a contour line, it signals that as you move in the direction the ticks are pointing, you will be descending in elevation. This can significantly influence route planning and tactical decisions in the field, making it crucial for soldiers to understand and interpret these symbols correctly.