Grid line bubble
Labels one of the building's grid lines, the reference lines that locate columns and walls.
How to read it
Under the A/E/C Graphics Standard the grid locates structural columns, load-bearing walls and shear walls, and is the basis for dimensioning. Vertical grid lines are numbered left to right at the top; horizontal ones are lettered bottom to top at the right, without the letters O and I, which could be read as 0 and 1. A column halfway between lines 2 and 3 is 2.5. Vermont's transportation agency uses the same grid bubbles to identify truss members on its bridge drawings.
Also searched as: column grid, grid marker.
This explains what a symbol represents on a drawing. Conventions vary between firms and standards, and a drawing's own legend takes precedence.
Read next
- Next in Blueprint symbolsStairsA staircase, seen from above. The arrow shows the direction of travel from this floor, labelled with the direction and the number of risers.
- The same shape in Barcodes and QR codesGS1 DataBar (produce sticker barcode)GS1 DataBar is a family of narrow barcodes for items too small for a UPC or EAN. On a produce sticker it is the small stacked barcode beside the PLU number, carrying a 14-digit product number.
More blueprint symbols
The same shape elsewhere
Browse symbols drawn with circles, 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. 3.3.1
- CADD Drafting Standards Manual, Section 7, Vermont Agency of Transportation, sec. 2.7
Researched, edited and approved by Rory Hansen before publishing. Last reviewed September 24, 2026. How we research
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