Dimensioning conventions — line that carries the arrows and value Which line type is drawn with arrowheads at both ends and indicates the direction and extent of a dimension on a drawing?

Introduction / Context:
Clear dimensioning ensures that a part can be built and inspected without ambiguity. Different line types each play a specific role: some define the measured span, others show where the measurement starts and ends, while others point to notes or locate centers. Knowing these roles avoids misinterpretation.

Given Data / Assumptions:

• Standard drafting conventions (ASME Y14 or similar).
• Arrowheads are used to terminate certain lines to indicate measurement limits.

Concept / Approach:
A dimension line carries the numerical value and is terminated by arrowheads, slashes, or dots that touch the extension lines. Extension lines originate from the feature being measured and extend toward (but do not touch) the dimension line itself. Centerlines mark axes and centers, and leaders point from notes to specific features.

Step-by-Step Solution:

Verification / Alternative check:
Open any dimensioning standard: the diagram labels confirm that the line with arrowheads and the number is the dimension line, while extension lines anchor it to the geometry.

Why Other Options Are Wrong:

• Extension line: does not carry arrowheads at both ends; it extends from the feature to the dimension line.
• Arrowhead line: not a standard term.
• Centerline: long–short–long pattern indicating centers, not dimensions.
• Leader: a thin line with an arrowhead or dot pointing to a note, not spanning a measured distance.

Common Pitfalls:

• Placing the dimension text on the extension line by mistake; the value belongs on the dimension line.

Final Answer:
Dimension line