Interesting, thanks for posting.
There's actually a problem with the scribed line test as described:
The straightedge is ... turned end to end...This test will only ensure mirrored symmetry of the two halves. An "S" shaped edge would pass the test.
It may be the manner of speaking but I'm sure they mean (what I would say as) "flipped on it's long axis". As you say; end to end means something different to me ;-) The method is the same as many of us employ to verify our squares. We just use a known flat edge as a reference. Good stuff.
"A hen is only an egg's way of making another egg".
– Samuel Butler
Yep, that's how I do it Glenn.
Alas, the text is quite clear and continues...
... turned end to end so that the mark (A) is in contact with the face of the board at B end.The referenced picture (FIG. 4 - TESTING A STRAIGHTEDGE) shows the straight edge marked A to the left and the work board marked B to the right - so it does mean end over end, and not like opening a tall thin book (which method works only as well as the stuff is trued.)
Eric - great stuff. But what book is it from? I want the whole book.
AKA - "The human termite"
I got this from cornishworkshop.co.uk under galootishgleanings
They apparently are "Scans from 1920's annuals of The Woodworker magazine".
Another one I like is: http://www.fullchisel.com/alburnam2.htm#Plane%20Apps
I hope Sawmill will allow these links. If not, sorry.
Eric