Wrong on so many levels!!

[Herman]

Dave, are you teasing me?
You draw a line square from a flat edge. Flip the square over and the line your drew must be right up to the square. If not, the square is off. That simple. Even to you Dave.
Herman

[Dave Bagwill]

Hahahah........yes I was teasing you Herman.

[Kevin in California]

Herman I never knew that, I'll have to check out my round squares and see if the triangles match up.

[Herman]

Ok guys, you got me! But I was NOT WRONG!
Herman

[Dave Bagwill]

No, you were right on the money.
I had been reading an article that discussed levels, squares etc. and it was mentioned that, in the experience of the woodworker that wrote the article, the squarest square he depends on for checking squareness on other squares, is the big metal framing squares - even the cheap ones seem to be right on.

[Kevin in California]

Herman, all in fun you know it. I'm just jealous cause you are smarter than me.

[johnnyg]

It is possible to draw a perfect 90 degree line using a “not so square” square. Just takes a couple extra steps.