How a plane surface projects: In any principal view, does a plane surface always project either as an area (surface) or, if perpendicular, on edge as a straight line?

Introduction / Context:
Planes are ubiquitous—faces of parts, flanges, covers. Interpreting how a plane appears in different views is foundational to multiview drawing comprehension and layout.

Given Data / Assumptions:

• Principal orthographic views are used.
• We discuss planar faces (not curved surfaces).
• Standard visibility rules apply.

Concept / Approach:
A plane parallel to the projection plane appears in true size and shape (a surface). A plane perpendicular to the projection plane appears on edge (a straight line). If the plane is inclined, it appears foreshortened but still as a surface region (not a curve or point). Only a straight line perpendicular to the view can reduce to a point; a 2D plane cannot become a point in a principal view.

Step-by-Step Solution:

Verification / Alternative check:
Auxiliary views created parallel to the plane recover the true shape from a foreshortened appearance. Perpendicular alignment produces an edge view; intermediate tilts produce foreshortening—never a point for a full plane.

Why Other Options Are Wrong:

• “Reduces to a point” is a property of a line normal to the view, not a plane.
• “Becomes a curve” confuses planar edges with curved surfaces.
• First- vs. third-angle does not change geometric truths.
• Shape (rectangular vs. other) does not alter projection behavior.

Common Pitfalls:
Misinterpreting a very thin foreshortened plane as a line; forgetting that hidden edges may require dashed lines but do not change the type of projection (area vs. edge).

Final Answer:
Correct: a plane shows as a surface when parallel, or an edge when perpendicular