Break line
Shows that part of the object has been left out of the drawing, usually to fit something long on the sheet.
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
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.
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.
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, 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
Last reviewed September 24, 2026 by Rory Hansen. How we research