What is the termination symbol for an extension line?

The termination symbol for an extension line is an arrowhead. Extension lines are used in technical drawings to extend from a dimension line to indicate the boundaries of a feature being measured or referenced. The arrowhead signifies the exact point at which the dimension applies, directing attention to the specific area of the drawing. This visual cue is crucial for clarity, ensuring that anyone reading the drawing can easily understand the intended measurements and their locations.

On the other hand, options like a square, a cross, or a dot serve different functions in technical drawings but are not used as termination symbols for extension lines. A square might indicate a specific type of feature or component, a cross could denote an intersection or a reference point, and a dot might represent a point of interest or a point of reference, but none of these fulfill the role that an arrowhead does in marking the termination of an extension line.