Question

What are often used to define the edge or boundary of something?

Answer 1

Answer: lines

Explanation: Lines are used to define the edge or boundary of something. This lines define and surround the edges of the subject, giving it a shape. Example is a square, triangle, rectangular shapes.

Answer 2

Contour Lines.
A perceived line that marks the edge of a figure as it curves back into space. Contour lines are created by the edges of things. Contour lines are lines that surround and define the edges of a subject, giving it shape and volume