Centerline
A line of long and short dashes that marks the centre of a round or symmetrical object.
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 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.
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.
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, center 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