Aren't very square. I compared the $3 set (2", 3", and 4") HF steel squares
to the Starrett and all of these three had a hump in the blade. In the $7
set (4", 6" and 8") - two had similar humps and one was either tapered or
not 90 degrees. It steadily "fell away" from the Starrett blade.
This was simple inspection - but the light shining thru was very evident.
Whether they're good enough for woodworking is only opinion. I'm no
machinist, but I doubt they'd make it past the front door in any metal shop.
Only real surprise was that those inexpensive acrylic drafting squares were
so much better. The HF box said "Made in India"; that gave me hope that the
quality might be better than typical HF fare.
Guess this is a good example of "getting what you pay for".
Oh well - it was a $10 experiment... YMMV.