Projection lines or extension lines are usually drawn using:
Continuous thin line
Engineering drawing uses a fixed set of line conventions (as per the standard line types) so that anyone reading the drawing understands each feature without confusion.
Projection lines, also called extension lines, are the light lines that project outward from a feature to show exactly which points a dimension is measuring between.
Because their only role is to guide the eye to the dimension, they must be faint and unobtrusive so they never look like part of the actual object.
For this reason they are drawn as a continuous thin line, the same light quality used for dimension lines, hatching, and leader lines.
A continuous thick line (option 3) is reserved for visible outlines and edges of the object, so using it for projection lines would make them look like real edges.
A dashed thin line (option 4) means a hidden edge, and a chain thick line (option 1) is used for cutting planes, so neither convention fits an extension line.
Hence, the answer is Continuous thin line.
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(A) 5 (I) W
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Important Questions from Engineering Drawing
What is a polygon with 12 sides called?
Wiring diagrams, circuit diagrams and electrical installation drawings are examples of which of the following types of engineering drawings?
Which of the following is NOT an element of dimensioning ?
Which of the following drawing instruments is used to draw smooth curves/arcs?
_______ is a dimension that is essential to the functioning of the component or space that is generally shown with limits.
