How should extension lines be positioned in relation to dimension lines?

The correct approach in positioning extension lines in relation to dimension lines is that they should not touch dimension lines. This is established to maintain clarity and prevent confusion in the interpretation of the drawing.

Extension lines serve as visual connections from the dimension line to the point that is being measured or referenced in the drawing, and keeping them separate helps delineate the dimensional information clearly. By ensuring a gap between the extension lines and the dimension lines, drafters can accurately communicate the measurements without misinterpretation, which is crucial in carpentry and millwork where precision is key.

Other options suggest forms of interaction that could compromise the readability of the drawing. Touching dimension lines could cause confusion over which measurements are applicable, while crossing lines could lead to a cluttered and unclear illustration of the dimensions. Replacing dimension lines with extension lines would eliminate the critical information that dimension lines provide about the measurements, rendering the drawing less useful for both understanding and execution.