On 11/24/2009 01:46 PM, Bill wrote:

The only "test" I can think of is the one I learned for a carpenter's
squa You use the square to draw a perpendicular line to the edge of a
board, then you flip the square over and draw another line. The lines
should be the same or parallel. Repeat several times for higher
confidence. How does that test measure-up here???

If you don't already have a known-good square, then that test works.
You need to make sure that the edge you're referencing the square
against is straight. If you're using a wooden surface, a knife will
give a finer line than a pencil.

If you've got a known-good square (a drafting triangle works fine) then
take it and the one being tested and place them both facing each other
against a known-straight edge. Hold it up against a light and see how
big the gap (if any) is between the two blades.

Chris