What type of lines help to establish the proportions and scale in a drawing?

Projection lines are essential in graphic communication for establishing proportions and scale in a drawing. They serve as construction lines that help visualize the relationship between different views or elements of a design. By extending lines from one view to another, projection lines ensure that the dimensions and angles are consistent, maintaining accuracy in the representation of the object.

In technical drawing, projection lines facilitate the process of creating orthographic projections, where multiple views of an object are depicted. This allows the designer or viewer to understand the spatial and dimensional relationships between components. By maintaining a clear relationship with the original object, projection lines play a crucial role in ensuring that the proportions and scale appear correct when interpreted from various angles.

Dimension lines, on the other hand, are specifically used to indicate measurements within a drawing rather than to establish the proportions themselves. Solid lines represent actual edges or outlines of objects, and dashed lines typically denote hidden features, which do not directly help with establishing proportions in the same way projection lines do.