Final answer:
In technical drawings, 'phantom lines' are used to show where parts of the drawing were broken off in a jagged manner, illustrating features that may not be visible in the current view.
Step-by-step explanation:
The type of line used in drawings to show where a portion was broken off in a "jagged" manner is known as a phantom line. Phantom lines are used in technical drawings and design to represent a feature that is not visible in a particular view or to indicate a moving position, adjacent positions of related parts, or paths of motion. This is important because line quality has a significant visual impact on how a line is perceived, with different types of lines conveying different visual movements or feelings. For instance, hard-edged, jagged lines suggest a hard staccato movement, which is in contrast to organic, flowing lines that create a more comfortable and natural feeling.
Understanding the use of various lines, like phantom lines or hatching, is essential in fields like engineering and architecture where technical drawings serve as blueprints for creating objects and structures. Recognizing how these different lines function aids in the accurate interpretation and construction of the objects being represented.