What type of break line is typically thick and freehand zigzag?

The type of break line that is typically thick and freehand zigzag is the short break line. This line is utilized in engineering drawings and technical illustrations to indicate that a part has been broken out for clarity, usually to shorten the part without altering its scale. A short break line helps to represent sections that would otherwise be too lengthy to display fully on the drawing, allowing designers to effectively communicate dimensions and features of the object without overwhelming the viewer with unnecessary detail.

In contrast, a long break line is often longer and straighter, and it's used to signify a substantial cutaway or to depict a portion of an object that isn't necessary to see in order to understand the overall design. Extension lines are utilized to indicate where a dimension line extends or relates to a part, while centerlines are used to highlight symmetry or specific axes within technical drawings. The nature of the short break line, particularly its thickness and freehand zigzag pattern, distinguishes it as the correct choice in this context.