Dimension line
A line carrying a measurement: the distance between the two points its ends touch.
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
In the A/E/C Graphics Standard dimension lines show a linear measurement, with the figure above the line and the ends marked by slashes at 45 degrees or filled arrowheads. The Navy's blueprint reading course ends dimension lines in arrowheads.
Also searched as: dimension string.
Differences by trade
The Navy course breaks the dimension line to fit the figure, except in architectural and structural drafting. Architectural drawings to the A/E/C standard keep the line whole, with the figure above it. Older practice broke it too: Wyatt's 1920 textbook describes the usual dimension line as a fine solid line broken for the figure at its centre, with an arrow at each end.
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, secs. 4.3, 5.5.1, 5.5.3
- Blueprint Reading and Sketching, NAVEDTRA 14040A, Naval Education and Training Command, U.S. Navy, ch. 2, dimension lines
- Blue Print Reading: Interpreting Working Drawings, E. M. Wyatt, 1920, Bruce Publishing Company, Milwaukee (Internet Archive), Arrows
Last reviewed September 24, 2026 by Rory Hansen. How we research