Design Nomenclature / Systems & Spec

Line conventions

Also called alphabet of lines, line types, hidden line, centerline, dimension line, leader, extension line

The graded weights and dash patterns that carry meaning on a drawing: thick continuous for visible edges, dashed for hidden ones, chain-dot for centrelines and axes, thin continuous for dimension and extension lines, and a leader arrowing a note to the feature it describes. Weight is information, not styling.

One dimensioned part annotated with each line type in turn: thick visible outline, dashed hidden bore, chain-dot centreline through the hole, thin dimension lines with arrowheads between extension lines, and a leader running from a note to the chamfer it describes.

In practice

Flattened to a single weight by CAD defaults and by anyone exporting to SVG. A drawing with uniform strokes still prints — it just stops distinguishing an edge from an axis.

Not to be confused with

DatumA theoretically exact reference — plane, axis, or point — derived from a real feature and used to orient and locate everything measured from it. Datums are ordered primary, secondary, tertiary, and that order is the inspection setup: change it and identical tolerances measure differently.

How this term connects

Related Confused with

In practice

Not to be confused with

Related

How this term connects

Referenced by