Line art is arguably the most fundamental mode of human visual expression and structural design. Long before the advent of full-colour rendering, photorealism, or complex digital painting, the simple act of dragging a pigmented tool across a surface served as the primary mechanism for translating the three-dimensional world onto a two-dimensional plane. A line can denote a physical boundary, describe a volumetric form, imply kinetic movement, and evoke profound psychological emotion. However, the apparent simplicity of line art is highly deceptive. Mastering the line requires a confluence of biomechanical control, an intimate understanding of physical tools and substrates, and a deep historical awareness of stylistic evolution.