A line is a continuous mark made by a pencil, brush, pen or other tool. Lines can be thick or thin, straight or curved, jagged or smooth, light or heavy. In architecture, lines are often suggested by the structural materials designers choose for their buildings such as the random lines of natural stone or the sleek lines created by beams of steel or walls of glass. Modern buildings often use bold lines created by structural steel cross bracing. Lines can also be suggested by the shape and massing of a building. For instance, a building can look horizontal or vertical.

Description sourced from architeacher.org. Image sourced from Design Stack.