Break line
Shows that part of the object has been left out of the drawing, usually to fit something long on the sheet.
How to read it
Break lines show that only a portion of a drawing, or a partial view, is shown (A/E/C Graphics Standard). The Navy's blueprint reading course explains that a break means a considerable part of the middle is presumed to be removed, and draws long breaks as ruled lines with freehand zigzags. In the Army's print-reading manual the dimension still gives the true length, and the short break line changes with the shape and material.
Also searched as: long break line.
This explains what a symbol represents on a drawing. Conventions vary between firms and standards, and a drawing's own legend takes precedence.
Common misreadings
A break isn't damage, and nothing is to be cut. As Wyatt put it in 1920, the draftsman doesn't want the workman to make the object broken as drawn; the break is a convenience for the draftsman, most often used to save drawing space.
Read next
- Next in Blueprint symbolsDimension lineA line carrying a measurement: the distance between the two points its ends touch.
- The same shape in Resistor color codesZero-ohm resistor (one black band)A resistor marked with one black band and nothing else is a zero-ohm resistor: a link in the shape of a resistor, with a resistance close to zero. Black is 0 in the color code.
More blueprint symbols
The same shape elsewhere
Browse symbols drawn with 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, break lines
- Construction Print Reading in the Field, TM 5-704 / AFM 85-27, Departments of the Army and the Air Force, para. 1-3i
- Blue Print Reading: Interpreting Working Drawings, E. M. Wyatt, 1920, Bruce Publishing Company, Milwaukee (Internet Archive), Ch. VII, breaks
Researched, edited and approved by Rory Hansen before publishing. Last reviewed September 24, 2026. How we research
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