What is the name of the line that appears as "- — - — - — -"?

The line that appears as "- — - — - — -" is known as a centre line. Centre lines are used in engineering and technical drawings to indicate the axes of symmetry or the centers of circles and circular features. They serve an important role in demonstrating the geometry of objects being represented, making it easier for engineers and designers to convey how parts should relate to each other in assembly or fabrication.

Centre lines are characterized by their alternating long and short dashes, which help distinguish them from other types of lines on a drawing. This distinct pattern allows anyone reviewing the drawing to quickly interpret which features are symmetrical or centered without confusion.

In contrast, hidden lines, represented by a series of dashed lines, indicate edges or surfaces that are not visible from a particular viewpoint. Construction lines are typically light and used as guides for drawing and laying out other features, while dimension lines provide measurements of features and include numerical values but do not use the same dash pattern as centre lines.