Originally Posted by
johnny means
This doesn't necessarily prove square, it only proves out of square.
I think that if you make sure the lengths of the parallel sides are exactly equal, the diagonal measurement will prove that something is square. If the parallel sides are not of equal length, you can have equal diagonal measurements and the panel will not be square.
So in your picture, if the top line and the bottom line are exactly equal length and the two lines on the sides are exactly equal length, equal diagonal measurements will prove square.
Mike
Go into the world and do well. But more importantly, go into the world and do good.