An
Improvised Square.
by Ronald E. Thompson 5/30/2011 A quick
and dirty square when you have no other is a piece of paper.
Fold a sharp crease...  ...and
then fold another while aligning the first folded edge to itself.
Perfect 90 degrees.
 Of
course there is no such thing as perfect. The longer the first crease
(and the better you align it), the more accurate the angle.
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