I need a good 9x12 imperial square

[steven c newman]

assembly start.JPG
Mine in use...for assembling frame and panel sides to a Chest of Drawers..
rail dry fit 1.JPG
Including a dry fit, or two...
Porch Projct, new square.JPG
mainly for jobs this larger square won't quite fit into..

[lowell holmes]

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