Question

Lines that appear to follow the boundaries of a slice or cross-section of a three-dimensional form are called:

Answer 1

These lines are called cross-contour lines.
Cross-contour lines are used in making nice pieces of art but most importantly they are a huge helping tool. These cross-contour lines can help people understand the solid form and the appearance of object from different perspectives and vantage points. Thus they are invaluable learning tool.