Hidden line
A line of short, even dashes: an edge or feature that is there but can't be seen in this view.
This explains what a symbol represents on a drawing. Conventions vary between firms and standards, and a drawing's own legend takes precedence.
How to read it
The Navy's blueprint reading course draws hidden edge lines with short dashes to show hidden features of an object. The A/E/C Graphics Standard uses hidden lines for the hidden features of a part or object.
Also searched as: dashed line, hidden object line.
Look-alikes
A centerline alternates long and short dashes.
More blueprint symbols
Sources
- A/E/C Graphics Standard, Release 2.2, ERDC/ITL SR-23-1, U.S. Army Engineer Research and Development Center, CAD/BIM Technology Center, sec. 4.3
- Blueprint Reading and Sketching, NAVEDTRA 14040A, Naval Education and Training Command, U.S. Navy, ch. 2, hidden lines
- Blue Print Reading: Interpreting Working Drawings, E. M. Wyatt, 1920, Bruce Publishing Company, Milwaukee (Internet Archive), Lines
Last reviewed September 24, 2026 by Rory Hansen. How we research