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How is a parallel straightedge used in drafting?

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Figure 1: Two techniques of representing an object. (A) Perspective drawing, suggesting that the object is cubical. (B) Orthographic top and front views, revealing that the object is not cubical. — drafting Figure 1: *Two techniques of representing an object.* (A) Perspective drawing, suggesting that the object is cubical. (B) Orthographic top and front views, revealing that the object is not cubical.

In the context of drafting, a parallel straightedge serves as an alternative to the T square.1

While the T square is traditionally used to establish a horizontal reference on a drafting board, the parallel straightedge is designed to be moved across the surface of the board while maintaining a consistent orientation. This allows drafters to draw accurate horizontal lines across the drawing area with greater ease and efficiency.21

Modern advancements, such as the drafting machine, have further evolved this concept by allowing the straightedge to be moved while maintaining any desired angle relative to the edge of the drawing board, effectively combining the functions of multiple traditional tools like triangles and protractors.1