# Mystery Mark on Swanson Speed Square



## mitch28311 (Feb 9, 2017)

I have several 6 inch speed squares, don't exactly know why but I do. On the long edge, there is a vertical line inscribed in the metal that passes through the 5 inch marker on one edge and the 80 degree protractor scale on the long edge. 

Does anybody know what this mark is for?


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## woodnthings (Jan 24, 2009)

*mystery mark*


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## d_slat (Apr 10, 2012)




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## Jim Frye (Aug 24, 2016)

Well, my Johnson 6" speed square doesn't have that mark, but my Swanson 12" speed square has a similar set of marks running from the 75 degree mark over to the side like yours. Now according to the Operator's Manual (what? you didn't keep yours?) the line is used when laying out birds mouths on rafters (pages 15 & 16).


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## mitch28311 (Feb 9, 2017)

Thanks for the reply. I lost my manual many years ago. I didn't find that reference in the on-line manual for the 6 inch square, perhaps that is too small for the long cuts for hip rafter seat cuts, but would therefore be included in the manual for the 12 inch version.


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