Centerline
A line of long and short dashes that marks the centre of a round or symmetrical object.
Easily confused with
How to read it
The Navy's blueprint reading course draws center lines as long and short dashes, alternately and evenly spaced, with a long dash at each end, for the centre of a circle, arc or symmetrical object. The A/E/C Graphics Standard uses the same line for the travel of a centre, and allows a short centerline to be drawn unbroken where it can't be confused with another line.
Also searched as: center line, CL.
This explains what a symbol represents on a drawing. Conventions vary between firms and standards, and a drawing's own legend takes precedence.
Look-alikes
A hidden line has short dashes only. The A/E/C standard also uses the centerline pattern for match lines, which show where a drawing continues on another sheet.
Read next
- Next in Blueprint symbolsHidden lineA line of short, even dashes: an edge or feature that is there but can't be seen in this view.
- The same shape in Smoke and CO alarm soundsLow-frequency 520 Hz alarm (sleeping rooms)A fire alarm in a sleeping room that sounds a low buzz in place of a high-pitched beep. It is the three-beep fire alarm rhythm at 520 Hz, which NFPA 72 requires of alarms provided to wake people in sleeping areas.
More blueprint symbols
The same shape elsewhere
Browse symbols drawn with letters and numbers or lines.
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, center lines
- Blue Print Reading: Interpreting Working Drawings, E. M. Wyatt, 1920, Bruce Publishing Company, Milwaukee (Internet Archive), Lines
Researched, edited and approved by Rory Hansen before publishing. Last reviewed September 24, 2026. How we research
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