I'd be looking for something that stays accurate, as in not being able to shift it
a few degrees out.
I'm not sure if I can move the engineers square, not that I've needed to.
I also got fooled before by my carpenters square doing this operation
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So glad I bought this engineers one for a tenner,
bought a cheap roofing square for the same money, going to true up any inaccuracies, and get a more refined edge, with a common lawnmower file (single cut teeth or farmers own) file should do the trick for the most part, and a square block of timber to register with the file.
Must look up how cheap you can get a huge 300mm engineers square for,
don't mind if it's not the best, as it should be good enough to deem worth making true in all orientations.
The trad carpenter squares blued spring steel is nice for using as a straight edge, and the end of the blade is also useful for cleaning glue off the bench, should you round the corners of them with a hone,
I've only just done that to mine.
A quick lift or pivot from horizontal to vertical makes a nice
teeny profile in a few swipes.
A handy tool to have around also.
Tom