I need a good 9x12 imperial square

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Mine in use...for assembling frame and panel sides to a Chest of Drawers..
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Including a dry fit, or two...
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mainly for jobs this larger square won't quite fit into..

https://www.homedepot.com/p/Empire-8...00/100148335An easy check is to draw a line across a board and then flip the square over and check the line. If it checks, you are square.
If you check and it is square, but you don't have parallel lines, you have other issues.
I have had good luck with these squares.

https://www.lowes.com/pd/Swanson-Too...Square/3047988

Also check this

https://www.homedepot.com/p/Empire-8...-100/100148335